Espruino JavaScript
Is Espruino right for my project? #4322
Replies: 2 comments
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Posted at 2015-01-07 by @gfwilliams I've just taken a look at the datasheet, and it looks like you'll have trouble using SPI. You need 4 data lines to change at the same time, so about your only choice is bit-banged IO. As of the very latest version 1v72, Espruino can run code in an interrupt, as long as it's written using the inline assembler, so it would be possible to get a very steady high-speed update out of it - as well as using WiFi and drawing graphics. I could provide some example code for that if needed. I have a side-project that would allow you to 'compile' JS code and run that in an interrupt, but that is probably still too far off being useful at the moment. Having said all that, it is a bit of a faff. And while you could get the update speed high enough, the animations would still pause a little when you did an HTTP request. You might find that you can get good enough using node.js with the WiringPi wrapper on a Raspberry Pi. If you can get the updates smooth enough then the multi-tasking on it would really help you out. Posted at 2015-01-07 by russdx Yup 4 lines which are 2 clocks and 2 data out lines which 2 SPI interfaces would cover? Can I not use the 2 SPI interfaces on this board at the same time? I have used hardware SPI to clock out dot matrix data in the past it works well :) I looked at Raspberry Pi But they only have 1 SPI I really need 2. I have no problem writing the core display update code in asm as long as its interrupt driven. Edit: I can offload the display update work to this board I am hoping the i2c interface is supported on it though as I don't think uart will be quick enough to send all the pixel data. This is also open source so I can edit it to support i2c if not supported (They have a i2c header) Posted at 2015-01-07 by @allObjects @russdx, doing things directly - without intermediate or sub controller - in javascript can become quite demanding... not just from a processing/cycle point of view, but also from a memory consumption point of view. The combination of driving a decent sized display and driving it over SPI pushes the envelope. As @gfwilliams points out, there is always the option to become a sub and dive into assembler for selected operations. Even with a SPI driven sub controller - such as IL9341 controlling a 320x240px color LCD - updating the LCD becomes a challenge when Espruino has also to do some processing at the same time. For example, receiving GPS sentences, parsing them, and updating the display required me to go for optimizations, such as partial and staggered/skewed updates, in order to keep up with the 1Hz GPS data rate... most of the time :(. For code and video clip see uBlox GPS and 320x240 TFT LCD w/ touch screen post. There is though hope for you: In my case, Espruino does A LOT of processing - even heavy graphical processing: it generates the font... You may also look at my other posts related to driving the LCD. Your suggestion to go with the PLT-2001v1 - which notably is a dedicated processor AND runs already at 100MHz (vs. 72Mhz) - looks to me the way to go. This is not at all to put down Espruino, but specific bit banging and memory buffering tasks is - imho - not what Espruino as a board and as a language/SW environment is targeting. What it though does in combination with sub controllers handling those tasks, is the quick and easy programming the overall control job. Passing on/thru of larger data amounts though has to happen in streaming mode. Receiving an update of a 192x32x3 bit 'image' is close to 2.5KB and quite a lot for a store-and-forward. Im sure you have control over how your updating server can deliver the 'image' data and you could break it up in chunks. PLT-2001v1 would have to have at least a 2-page buffer capability to have not garbled display while the update is underway. Alternative for temporary storage I use a F-RAM / Fe-RAM / M-RAM technology, which has the advantage of no wait cycles over the use of SD cards. Posted at 2015-01-08 by @gfwilliams @allObjects in your case the slowness was from driving a 320x240x16 bit display. This is only 192x32x2 bit so the amount of data is far, far lower. The controller board might be a good plan though - as it seems it'll handle multiple panels it might take a lot of the pain out of the updates. How exactly did you plan on doing your 24fps animation? Is it:
I guess the first one could be a bit tricky, but second should be fine to do. Having said that, if you've got a controller board then you could just use a Pi - there would be more setup in terms of fiddling with the OS, but a bit less wiring as network is effectively built in. Posted at 2015-01-08 by russdx Basically I have written this live train departure board in js using the canvas. I want to know display this data on a real dot matrix (the ones i linked to) I was under the impression espruino would be able to basically run this code standalone but instead of seeing it on a html page i will just copy the canvas pixel and convert to byte array and send them to the dot matrix driver board. (when animating it runs at around 24fps and the scroll is 12fps) Once done it should not be connected to a pc. It should run 100% standalone and get its data using wireless and then send the data to the dot matrix driver board. I wrote this project is js because i like using the canvas for graphical projects its easy to set pixels and so on. Maybe i should of just wrote it in .c and made a byte canvas and but then I would need to implement all the (comes for free with js) canvas methods like drawing and buffers and so on. Also there is no font rendering going on that font is a custom (exact map of network rail font) but stored as my own format and i decode and draw it my self. Its not using canvas text. Another quick question :) Posted at 2015-01-09 by @gfwilliams The train time page looks really neat... Is it actually for someone, or is it just a personal project? Yes, Espruino could do the animation just fine and push the pixels - but the graphics library doesn't have the same API as Canvas (on quite a constrained device, the whole stroke/fill stuff doesn't really make that much sense). There's support for custom fonts - see here. You'd just have to put your font into the required format, which shouldn't take long at all. Then it's just a matter of using The only thing I'd say is to queue the HTTP request after the 'train stops at' has gone offscreen. That way if there's a delay it won't be visible to the user (unfortunately when looking up a domain name, Espruino usually has to block while it's resolved). If you want to use C, the easiest way is to just get Espruino's source code and then add your own source file, which can provide objects + functions that JavaScript can then use. You can compile C code on your PC and then dynamically load the compiled code into memory and register it as a function using I doubt you'd need to do any of that though. Worst case is you have to do some fiddling around with the data from the graphics library to get it into a format that'll work with your display, but I think that'd be pretty easy to do quickly. Posted at 2015-01-09 by russdx Just a personal project using the network rail LDB api. I take the train from bristol to reading every day for work so its nice just to see what the next trains I can take are / delays / cancellations etc.. My canvas only uses fillRect (just to draw a 1x1 pixel and drawImage (to copy different canvas's around) Is all this supported? I think I will use that dot matrix driver board to drive the displays as all the code has been written and I can just plug the displays directly into it. Will save me a lot of time and effort hehe. (so will not need to write any dot matrix driver stuff my self hehe) I read in another thread of yours we can run espruino on a rasp pi? I have one of the new A Plus models so was thinking run my little app on that and have it talking i2c to the dot matrix driver board. This way the rasp pi can take care of the networking and js canvas side and the dot matrix can take care of the display updates. Posted at 2015-01-09 by @gfwilliams Yes, that should work - those are more or less the same, although drawImage may not be able to take 'graphics' as an argument. See http://www.espruino.com/Graphics for some examples. I'd really suggest you use the built-in custom font stuff though - it'll make your life so much easier. I'm not sure anyone's written any interface code to link the driver board to Espruino, but it should be pretty simple to do. Espruino can run on the Pi, yes - although there's no I2C support in it yet. I have to focus on the Espruino board which people actually pay me for, so I'm kind of reliant on others to contribute code for other boards - and there are only a handful of people that do unfortunately. There is serial port support though, which in many ways is better as it's totally asynchronous. There's also node.js on the Pi - although I'm not sure what the situation with the Canvas is - I guess there must be something. Posted at 2015-01-09 by russdx Yeah I see what your are saying, I am trying to keep the code this way so I can still run the js in a normal browser and have it work as is. I might have a look at writing the i2c Rasp Pi stuff because I will need to use this. I don't think i will be able to send all the frame data at 24fps over serial? I have looked at node.js and there are a few canvas modules I can use. I might look at rewriting it not to use the 'canvas' at all for the internal animations and just use my own byte array to store the pixel data. Then just have a switch for if its run in browser mode or on device. When on deivce it just sends the byte canvas directly to the dot matrix driver (in correct format) or if running in browser just draw my byte canvas onto a js canvas. I will see what I get away with before I make this move hehe. Posted at 2015-01-09 by russdx The dot matrix board serial is 115,200bps If my math is correct this is far to slow for me to run 24fps :( 192x32x2 = 12288 bits
This is why I will need to use its i2c interface (hopefully been written or I will be downloading the pic dev tools as well hehe) Posted at 2015-01-09 by @gfwilliams Yes, 115kbps does seem a bit slow for a nice animation. However on the datasheet for the controller I see no mention of I2c (apart from a note saying it might be added later). By far the easiest thing to do would be to just increase the serial baud rate to 2M baud and then you're sorted. However now I'm on the datasheet I don't see a way to send raw bitmap data to the controller either - so you may be out of luck there too. It might be better to just use WiringPi on node.js on the Raspberry Pi to bit-bash the data directly to the LEDs (without the controller). It's worth a try - it may just work without being too glitchy. Otherwise you could try a similar thing with the Espruino board - the more I look at the Embedded adventures one the less convinced I am. Posted at 2015-01-09 by russdx It comes with full source code. So at the very worst I will just add in the i2c part my self. Or maybe up the uart? How fast can PIC uart hardware go? Like you said would also need to add some way of sending raw pixel data as well. So Cant really use this project out the box but I think it will still save me a lot of work even if I just wrote the firmware from scratch! Unless I can get the dot matrix driver code hardware timer interrupt driven on Pi or Espruino it will be jumpy I think. Maybe writing a small c class that runs the dot matrix display with hardware timers on the Espruino might be the way forward? and send it the frame data from the javascript This was one of my other projects It used very similar hardware to yours the STMF4 which is a powerful arm chip and when running the display just off software delays with the usb running as well the display was jumpy. I had to put the display update in a hardware timer driven routine to force it having priority and this solved the problem. Hopefully would be the same with the Espruino. Least I got a few routes to go down :) Posted at 2015-01-09 by russdx Reading the PIC32MX450F128H datasheet (quite a nice little microcontroller actually hehe) Says Hopefully I can just bump the UART to a faster speed and use this. How fast can I send data using the Espruino UART? Posted at 2015-01-09 by @gfwilliams Yes, bumping the UART seems easier. The STM32 will do at least 4mbps I think. Hopefully more than enough for the controller. Just to add, if you're using Espruino the speed of JS execution isn't anywhere near as good as C. Using the built-in font code is likely to be 100x faster than writing your own. If you wanted the code to work the same it'd be pretty easy to just write something like: Love the pinball display by the way - very cool. Doing everything in Espruino with hardware IRQs is definitely an option though. I'd be interested in helping out however I can - it'd be a huge help to be able to do that kind of real-time scanning, if only for all the charlieplexed stuff that's out there now. Posted at 2015-01-09 by russdx Trying to think of easiest way to convert my current text method I current have these params function drawText(str,ctx,font,colour,x,y,width,align,spacing,debug) Do you support align? As long as the javascript can run my canvas at 24fps thats all I need :) Posted at 2015-01-09 by russdx Edit: added my textManager Attachments: Posted at 2015-01-09 by @gfwilliams There's no align built in, but it's easy enough to use stringWidth and then do what you want with it. I usually do something like: Otherwise it looks like you can just replace your code under Posted at 2015-01-10 by russdx Perfect :) I will convert that over. And all this sort of code will run quite happily? Posted at 2015-01-10 by @allObjects This is not gona work... :(... Espruino is a server like context... window and document (global variables) are undefined, as are all the other view oriented browser global variables... With Espurino it's more like a node.js or Rhino environment... If you want your code to work unchanged, you have to come up with the emulation of these things. --- And like your idea to have it run anywhere... (I did the same for some stuff: developed in the browser emulating Espruino context, and then move it over...). There is no html / view DOM, and therefore all these functions are not there. I did not look in detail into all of your code, but I think it is feasible. I'll sit down and will give you some pointers... until then, have fun with Espruino. Posted at 2015-01-10 by russdx Hey allObjects Yes I have just figured this out my self hehe, I wrote this in javascript thinking I could directly port it onto a micro because I had heard of them running javascript I should of done a bit more research hehe. My current plan is to rewrite all canvas code (I only use drawImage and fillRect) my self as byte arrays (very similar to Gordans graphics libary) I will slightly adjust my textManager to draw the font to the byte array canvas and instead of using drawImage (I was only use this as a canvas copy) I will create a canvasCopy method to copy chunks of one byte canvas to another. canvasCopy(orig,x,y,w,h,dest,x,y,h,w); This way I will now not be reliant on any canvas object and could very easily port this to plain .c if I needed to. My plan for the byte canvas (based on my pinDMD project) as I only need 3 colours I can get away with just (192322)/8 = 1532 bytes canvas array which will save on memory. But then again creating a canvas which support 255 colours (192*32)*8 = 49151 bytes is bit larger and would be better in-case i want to use more colours? I would convert this larger canvas byte array down to the compressed 4 colour version when sending data over i2c to the dmd controller :) I would also need to swap out the way my code makes http requests with the wifi hardware ones espruino. If I can get the core of this project just written in pure javascript I think I will be ok and can have a minifier create a web version and a espruino / or node js version (my code is in multiple files so this all needs to be put into one anyway I guess to work with espruino or node. Thanks for the help offer I will certainly take you up on that when I get stuck hehe :) Posted at 2015-01-10 by @allObjects Got called to special home cooked lunch... that's about the only thing that creates an interrupt of higher priority... ;)... back to business. Developing with Espruino the way you do in a browser gets you straight into out-of-memory hell... or, what happened to me using the module folder with google closure compiler service 'too many compiles'. There are several ways code can be loaded to Espruino: either direct in code or as module using require. With require you stick your code as a module into the modules folder as definable in the Web IDE. The advantage there is that code is (more) optimized when uploaded and uses much less memory... Also Espruino is different from any other JS virtual machine (VM) runtime environment in the way that it runs of the source: there is no Just In Time compilation into some internal VM (byte) code for execution... (therefore keep comments outside of functions... i like inline comments..., makes the code meta-readable). Anyway. I would not make to much changes in your code... I would think of the canvas / context as a facade/adapter of either Espruino's Graphic library or as the controller board you intend to by by. I do not know which hardware you already have... Display? Controler? I'm sure though you have an Espruino 1.3b or 1.4 board that you run with Espruino 1v71 firmware, do you? In the development process you start with the code in the Web IDE editor emulating a module and with very small buffers - just to get the algorithms going - and then, when it runs satisfactorily, you put it as module into the module folder and use the full buffers. This way you can develop and test nicely, and later run optimally in speed and as much application data memory as possible. Btw, have you ever heard of require.js? It is a way of develop javascript application in a similar modular way with dependencies as java or c/c++. What language other than javascript are you familiar with? Since we do not have an html page in Espruino, we quasi emulate the html page... I run the code from your ip address and looked at the html document. It is very simple: it is a single DOM node with the id canvas in which you create the canvas objects and... In the end you will will have exactly the same js files that you have now as modules and you load them with To emulate the DOM / document and Canvas, you crate two extra modules where you stick the objects and methods into so you can run exactly the same code that you run in the browser. As a first step, we have you get going on require.js... to load your js files with require. Then we Posted at 2015-01-10 by russdx The hardware I will be using is. How I control this I am still trying to decide hehe. I have ordered one of these. And raspberry pi I also have a few stmf4 dev boards lying around hehe. My three routes at the moment are run this javascript (converted version) in node js on a raspberry pi with a node i2c module and stream the data to the dmd controller board and have that take care of the dmd updates. (I will either modify or rewite the current firmware to use the i2c on the dmd board as im not 100% its supported yet) Or get it running on a espruino board (will buy one once I can confirm i can run some form of this code on one hehe) and then stream the data again using i2c to dmd board Or (I have experience with the stmf4) just write the code again from scratch in .c and bitbang the dmd my self. I would like to use my javascript though as a few people around the office like using this project and I would like to continue to add features to it and then be able to create a version I can port to my hardware dmd. I have little knowledge of node js I have wrote a few little scripts for it. If I am understanding you correct I can leave my project the way it is and use require js to load in the extra files and then override the canvas methods with my own custom byte arrays? I am currently 30% to converting the javascript canvas with my own byte array one so I think I will continue and finish this hehe. Least it removes the whole html canvas dom problem. Once that is complete I will be left with a project that has multiple files that will need to be loaded onto the espruino. How much ram does it have because my code does create quite a few little temporary canvas one being (200092)/8 large will this work at run time? Posted at 2015-01-10 by @allObjects JavaScript has typed arrays / buffers that allow a very compact usage of the memory. I guess it could work... but I would rather use the display controller's memory and just ship commands and other stuff over there. So every canvas operation would just pass on the command to the controller and the controller actually creates then the bit stuff for fonts, etc... I need more understanding... Btw, could you also 'publish' the php file that serves the ajax call? Posted at 2015-01-10 by @allObjects I'm not sure about the effort of conversion... even with a nice integrated development environment and a Espruino (or alike connected), there is not really a hot-swap possible. A single step is for sure there - @gfwilliams would for sure know. I use Chrome as my JS development runtime environment, Apache as my server environment, and some useful text editor (with less or more JavaScript and other support - such as TextWrangler...Brackets). I edit my files directly in a subfolder of Apache's Documents folder when using plain text editor/TextWranlger, Brackets has nice (preview) server integrated... Getting to a setup for a cross develpment makes it fun: you will be able to run the very same app on the browser as well as in Espruino with - in kind of .c terms - just to load different #ifDef'd header files... Since you care most about the Canvas and its context, emulating that is not much that is needed. Looking at your code I see that it is bottom line a set of functions. Making them objects would be my first step... it makes it more robust, easier to extend, and also easier to debug. I pulled all your files... notice that the departure board is the last loaded js file and is the driver... (like in an SPA...). It makes the ajax request and gets all the things going. I assume that you have some php that actually goes and gets the data, because I cannot see any cross domain enablement CORS in the html page... this allows you to go directly after the data sourcing server and you do not need to go through php as the proxy server to respect the browsers sandbox / same origin policy (for security/safety purposes). I also see that the departure board has DOM things in it... pulling this out makes it Espruino ready. So there is some restructuring to be done, but - imho - it is useful and very helpful for moving on, also with extensions. Since I do not have a LED panel, but I have a 320x240 TFT LCD display w/ touch screen, I'm thinking of making this my board and trying to get that done. I'm looking at my display as the canvas... so my adapter will take the Canvas commands/method calls and translate/adapt them into the Espruino Graphics methods/calls an run the same on my TFT LCD display as you run on your LED panel. The controller of my display has a scroll modus too - like the controler your thinking about - so refactoring/extracting the code and have it scrolled in code / canvas / screen controller is an interesting task. After all, the hardware and software are just subsystems communicating with each other. The interface stays the same, the implementation is platform dependent. Posted at 2015-01-10 by russdx Yes you are correct it talks to a php script that sits on my amazon aws server. This script actually makes the calls to the network rail LDBWS api and receives the data. I then rip out the parts I want and convert it to an json object and this is what is returned. I am using a naughty header('Access-Control-Allow-Origin: *'); to allow the javascript to talk to my php while developing from my local machine. My html literally just creates a canvas this is because the project was always aimed to just be run on hardware but people in the office liked it so much and use it for there trains I decided to try and keep it cross platform so they can still use it in the browser. If I am reading what you are saying correctly. You would be able to convert this to run on espruino but have a module that draws it onto your lcd. And I would then replace with a module that just sends the canvas data to my DMD board using i2c instead. I am still a little bit worried about about memory? all the little temporary canvas's will use up to much ram? If you could help me with this project I would really appreciate it :) Posted at 2015-01-10 by @allObjects Naughty header... ts...ts...ts... glad that you did not get found by some phisher... ;)... Do you need a key or account to access the network rail LDBWS api? - and what is the request / response format? rest/jason, soap/xml (or worse)? I see no issue why not go directly to the api than through your server (except you have a 'hidden agenda'/additional intentions - such as... of course a good one, I assume ;-). Posted at 2015-01-10 by russdx hehe yes just for development lol I will remove once complete lol This is the api Yes you have your own private key which is in the php file. Also some one made a php example of how to receive the data using SOAP so I just copied this and converted to json. That's all the php script does really :) You could talk directly from the javascript I guess but I have no idea how plus your key would be reviled. Posted at 2015-01-10 by @allObjects Now comes you php into place... because I'm sure that you can use it only so frequently before you run into terms and conditions that ask for money... :(... like with maps services with Google. Your server could make it easy to get a key and the key would be transparent... a user registers with the server and this gets the user a key, which will then be used for further reads by that user. Of course, this needs only be done when you run into the volume challenge. Posted at 2015-01-11 by russdx Yup I get 5 million requests to the api a month which when its just me and a few friends using it is ok :) Posted at 2015-01-11 by @allObjects Let's move back to the tech things. This are my thoughts: First step is to set the CORS definition in the index.html, make the access from any place to your server and later to the api, and scrub the response in the client. That means, the php would for the beginning just enhance and forward the request with the key and forward the response like a straight forward proxy. A url parm can keep the coexistency... &go=proxy and &go=api would be my suggestion for the new functionality. 2nd step wold be the separation of DOM oriented stuff in the code vs plain js stuff - we may end up with some more files - no problem. 3rd step is making classes (placing the variables and functions that belong together into a class definition or singleton). 4th step is moving onto require. These steps are all to refactor for cross platform enablement... And when you have an Espruino and the LED panel and processor, it will be ready. I for my part will make on my Espruino a Canvas that uses the Espruino Graphics and the IL9143 library. Posted at 2015-01-11 by @allObjects 5M - this will go a long way... Posted at 2015-01-11 by russdx Ah another reason for the php is if you have multiple destination states the php has to make multiple calls to the networkrail api it also has to make a separate request to collect the calling at stations data (forgot about this lol) then packages it all up in one friendly json response. If it is written to use require (to load the js files) does this still run inside a browser? I will do some research on this and try and implement it :) I have included the php file in this reply so you can see what it is doing. I guess it is doing quite a lot and saves the js from making multiple requests and just hides/removes all the train api crap from it which it doesn't really care about. It just wants to make one request and get back just the data it needs :) (way I see it hehe) Its not 100% finished I still need to sort out the station service messages. Attachments: Posted at 2015-01-11 by @allObjects Is https://github.com/railalefan/phpOpenLDBWS/blob/master/OpenLDBWS.php this the library/module you use in ldbwsService.php? Posted at 2015-01-11 by russdx Ah yes that is the file I have included in my php :) Almost converted html canvas to my own custom byte canvas just need to write the copyCanvas function now :) Spent ages trying to figure out why my chars where being clipped off. eventually found out that javascript bitwise shift right does not wrap??? and just fills with 0's useless! hehe. My led panels turned up today but one was damaged in the post :( hoping it still works but will see once driver board turns up hehe (embedded adventures says they will replace if not working 100%) which is good. Posted at 2015-01-11 by @allObjects @russd, got it running local accessing your ip for the data. Began the separation of concerns work... and at the same time grow the inner workings of the DepartureBoard.js... a bit a challenge since it is all global function calling... said that, I could must put all JS code into one single file and it would still work... ;-). Question: what is the particular reason to use a JS written JSON parser and not the native JSON object as provided by the JS environment? I use the the JSON.parse() with a responseText of yours, and it works just fine... Attachments: Posted at 2015-01-11 by @allObjects In Espruino's console, I made some initial memory tests. I set the Then I set the responseObect to the JSON parsed responseText: No code (except the variable references) - just the response string and response JS object use 377 variable elements of 2250, leaving 1837 for all the other things. A variable element is a number of bytes and is also a garbage collection entity (btw, strings are chained memory elements... so not contiguous memory bytes by definition, and therefore concatenation is quite 'simple' and effective) - Espruino has separate Web pages about implementation, performance, memory usage. This is from Espruino's Web IDE console: Attachments: Posted at 2015-01-11 by @allObjects Posted at 2015-01-11 by russdx Hey Wow that's pretty cool to see it running on the web ide :) Regards to the json parser I did not actually know there was a native one! I will definitely use it know I know it exists :) (I did come across it in node js and just assumed it was a node js thing did not know it was a standard javascript method hehe) I have almost got it working with the removed html canvas :) still working on that canvasCopy method (not quite working right lol) Hopefully finish it off tomorrow in work. But it still all runs fast and is looking good and is using pure byte arrays now :D not relying on html canvas which is nice if I ever wanted to port this to another language. Posted at 2015-01-12 by @allObjects Great to hear... what I though think is that the array/buffer part should be in a separate class. The way the code works now, is preparing everything in a buffer on bit level - actually rendering the characters - and then all that data - bit image buffer - is sent to the display system (Canvas). This may get short handed on memory, because the setup is not taking advantage of the display controller's buffer / memory and processing and function power (the controller implements quite powerful render operations, including scrolling). Refactoring the bit to buffer code into its own class enables it to be easily replaced with the display's buffer and code.. If the controller has not the desirable font(s) and no way to upload them, one character is rendered at a time and then shipped as a bit image... I know for sure that with a display with 16 bits of color (actually 24 bits when going through the Espruino Graphics interface) per bit and a much higher dot density than a LED panel, it is becoming a lot of bits... just as @gfwilliams mentioned (The display I have is a 2.8" diagonal TFT LCD with 320x240 pixels, a pixel density of about 138 dpi, where as with 5mm LEDs on the panel you end up with 5 dpi. Even with the adjustment of the viewing distance, dpi ratio is still between 3..5 to 1 for LCD vs. LED.) The display controller's buffer can be seen as the (or canvas / context) which understands most importantly text drawing commands: just sending the ASCII string together with foreground and background color information, font size information, and may be font type id, and position is sufficient. I know already for sure that I cannot have 3 bytes per bit in buffers if I want to run simultaneously also other code and and data in the main processor's memory. Posted at 2015-01-12 by @allObjects After some wifi connectivity skirmishes with the CC3000 module - see - I'n now ready to read data... this is the code I'm using: And this is the expected response - so far in the console... is:
The time is in [s].[ms] to give a feeling about the speed behavior:
The very very first request brought the response string in on shot. I then added the JASON.parse to the simple sample code as described in Clienbt paragraph on CC3000 Module page. In great anticipation... nope: all following requests brought only a very tiny fragment containing: {requestedA. That was all. Some more reading - notably from the overall Internet (HTTP) page - lead back to working code again. Even though it is only a single shot at data, I'm satisfied for now. More later. Posted at 2015-01-12 by @gfwilliams I'm afraid I don't have time to read through all of this right now - but in short:
Posted at 2015-01-12 by russdx If I use the the custom espruino graphics canvas how will it work when running in a browser? Also if I draw directly to the dmd controller board canvas how will this work inside the browser? I had a look at what that board supports and i dont think it supports enough to do what I need. (would need a new font for a start!)(and can you draw fonts half off the canvas?) Using my own (very simple) byte array canvas (it only supports drawText and copyCanvas) and will work in the browser and on a micro controller (I am thinking of using the stmf4? which definitely has enough ram for all my little byte array canvas's) Another reason is if i do decide to just straight port this and run in c on a micro controller I can pretty much copy and paste all my logic and canvas code I am not relying on a certain os canvas library. I spoke to embedded adventures and they say I can either bump up the uart or use the i2c (need to write bit of code my self) to send the frame data to the dmd controller board. Which is my preferred method. Its cool to see the espruino making and parsing the networkrail request though using that wireless board. One step closer :D Posted at 2015-01-12 by @gfwilliams
You'd have to write your own version of 'drawString' just for the browser - but you've basically done that all already.
It will, yes - but chances are it'll run too slowly to get the 24fps update you want on Espruino - unless you run it on something like a Raspberry Pi, or you re-write everything in C. Posted at 2015-01-12 by russdx Ah Even on Espruino running on a STMF4? I still like the raspberry pi idea. Posted at 2015-01-12 by @gfwilliams Yes, even on the F4. It's possible you could get something but it'd be a real struggle. Posted at 2015-01-12 by russdx Ah To be totally honest I have no idea what is actually happening under the hood when running javascript on a microcontroller. if you have a simple for loop in javascript is that not converting to a simple for loop in c? why does it run so much slower when written in javascript? Posted at 2015-01-12 by @gfwilliams Well, JavaScript is an interpreted language, rather than a compiled language. It means that no work is done 'up front' by a compiler. The way there's no type checking makes compilation quite difficult. On a PC, with something like Chrome and V8, it cheats - and when the webpage is loaded V8 does a lot of clever stuff and basically 'compiles' the JavaScript to native code every time a webpage is loaded. On other (often older) JS interpreters they compile the code to an intermediate form (like a bytecode). On Espruino there just aren't the resources to do that on the chip, so it actually executes the text strings your wrote directly - which makes it a lot slower. I'm actually doing some work on partially compiling the JS code up front using the Web IDE, but that's still some way off being useful. At the end of the day, it can still all be done, and can be done really easily using the built in Graphics class... but if you want to write your own new Graphics class then you're probably better off using something else like a Pi with node.js. Posted at 2015-01-12 by @allObjects I had a different thought... why not use the interface that the context of a html canvas has... the application talks in JS the same way to this interface whether running in a browser or in a dedicated micro controller. Based on that idea - but with the give Graphics library and the given's of @russdx's lcd panel controller api - I was thinking of an adapter that has on one side - the application side - the context api of the browser canvas and on the other side it speaks to the Espruino Graphics lib or the LED panel controller interface. For example: how much can the api for drawing a line (in a 2D context) be semantically different between any of the environments? Lets wrap the setting of fonts in an api as well that requires only to pass an ID and let the dedicated implementations - which are loaded with ID matching profiles - do the settings. Yes, it adds layers, but @russdx would like to run the very same (high) level application code on just any platform... @gfwilliams, no adversary thoughts here, just a question: could you imagine the Espruino graphics have the same api as the 2D context of an html canvas? Posted at 2015-01-13 by @gfwilliams
For drawing text, yes - for lines etc, it's possible but not without a lot of overhead (as the HTML5 Canvas lets you define a path, and then 'stroke' or 'fill' it afterwards). It'd be a lot easier to do as you say, but the other way around: Create an Espruino-style graphics object but on the PC (where you have enough resources for the adaptor). Posted at 2015-01-13 by @allObjects
...comes down to: Chicken or egg - what comes first. Being 'raised' on HW, it's the egg, being 'raised' on (Web) SW, it's the chicken... ;-). PS: There is no way not being biased... ...comes down to: Chicken or egg - what comes first. Being 'raised' on HW, it's the chicken, being 'raised' on (Web) SW, it's the egg... ;-). Posted at 2015-01-13 by DrAzzy That doesn't mean that it's as easy to fit the chicken into the egg as it would be to go the other way around ;-) |
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Posted at 2015-01-13 by @allObjects Created a wlan singleton that lets conn(ect), req(uest), and disconn(ect) with hiding the lower level details. The application code connects and then repeats requesting data every 10 seconds until stopped. Holding BTN1 down on upload enables (detailed) logging, and holding BTN1 down on display of the data (in the console) stops requesting data. Nice to see in the the log is the self recovery of the Espruino CC3000 module with a CC3000 power cycle when something is going down (badly...). This is console output, that shows a going down also on the very first request. This is the code (also attached as file): Attachments: Posted at 2015-01-13 by @allObjects ...did not go there yet... but thanks for the graphic comment. Nevertheless, I'll give it a try... PS: edited the referred to entry to take my and everyone else's bias into account... |
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Posted at 2015-01-07 by russdx
I have a little program written in javascript that displays information on a 192x32 pixel canvas. It also requests data from a php file on my server every min (So I will need WiFi, as I need the project to run standalone once complete).
Second part of this project is to display the javascript canvas on a real dot matrix display (I only use 3 colours) I am going to use three of these displays.
http://www.embeddedadventures.com/led_matrix_display_LDP-6432.html
To drive these displays you need some IO but for the data lines (x2) I want to use SPI to get the data out fast as possible. So I will need x2 SPI ports (Which are available) And I would like to use a UART based WiFi (As I need both SPI).
From experience I know driving dot matrix displays which need constant scanning to keep the image updated. You need a dedicated process to do this preferable running off a hardware interrupt timer so this process gets priority and the display will not freeze or look stuttery.
Does the js have access to these timers? Or can I write this part of the code in .c and send frame data to it from the js?
How fast is the SPI? same specs as the STM chip?
I have already written the project in javascript so would like to keep it in js. Any thoughts on if it would be possible to run it on this board. It needs to update the dot matrix at least 24fps.
Any thoughts would be much appreciated.
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