HD44780 module error

[espruino-discuss3]

Posted at 2015-08-23 by cwilt

I thought I would start playing with some modules today. The first one I tried was the HD44780 using the I2c example. When I try to run it I get this error.

This is the code...

I2C1.setup({scl:B6, sda:B7}); 
var lcd =require("HD44780").connectI2C(I2C1); 
lcd.print("Hello World!");

This is the error returned.

Uncaught Error: Field or method "print" does not already exist, and can't create it on undefined
 at line 2 col 7
4,e,e])}
       ^
in function "a" called from line 1 col 8
{a(51,1);a(50,1);a(40,1);a(12,1);a(6,1);a(1,1);return{write:...
        ^
in function "f" called from line 2 col 9
4,e,e])})}
         ^
in function "connectI2C" called from line 1 col 45
var lcd = require("HD44780").connectI2C(I2C1);
                                             ^
 at line 1 col 4
lcd.print("Hello World!");
    ^

Any suggestions?

[espruino-discuss3]

Posted at 2015-08-23 by @gfwilliams

Are you using an up to date firmware?

Looks like there should really have been an error about I2C timeouts before the one about print - I was pretty sure that's something that got fixed recently.

However I reckon the issue is that the display isn't wired up right. Maybe SDA/SCL are crossed over, or maybe they don't have pullup resistors on them? I don't think those displays have them built in.

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Posted at 2015-08-23 by DrAzzy

Do you get any errors if you leave off the lcd.print() command?

If so can you post that?

Also, do console.log(lcd) and see if there's anything there. I suspect the connectI2C() is encountering an error, resulting in there being no lcd object - so there's no print method.

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Posted at 2015-08-23 by cwilt

Turns out that my board uses a different IO expander chip. I then used parallel interface and it worked fine. Sorry for the mix up.

I am curious how you change the I2c address without editing the module as it seems to be hard coded in?

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Posted at 2015-08-24 by @gfwilliams

Interesting - do you have a link to the module? This is the first time this has come up.

You'd have to change the module I'm afraid. To be honest a different IO expander IC might well behave in a different way (or be wired differently), so changing the address might not be enough.

If you want to play around with getting it working, try adding exports={}; at the top of the RHS of the Web IDE, copy and paste in the existing module and do var lcd = exports.connectI2C(I2C1); at the bottom to test it.

You could then play around with a different address/different commands to see if it works. We could then put the changes back in (either allowing the address to be changed, or it more was needed, having a separate function for your new driver IC).

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Posted at 2015-08-24 by cwilt

Its the LCD backpack from adafruit.

I have a module in python that I wrote for it. Perhaps I can port it over.

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Posted at 2015-08-24 by @gfwilliams

Eep - yes, we should definitely support the Adafruit version. Actually it looks like this came up a few weeks ago, with *yet another IO chip in a module made by Adafruit!

http://forum.espruino.com/conversations/272048/

Adafruit has some Arduino code up for this one as well, at https://github.com/adafruit/LiquidCrystal

Looks like it'll have to be a new function, as the I2C commands are definitely different.

A connectMCP23008 function should be pretty easy though. i2c.writeTo(0x20,9,data) should handle the write once the IO direction is set.