Jolt serial comms... Grove Doppler Radar

[AndySmee]

I've run out of ideas to get the Jolt to communicate with the Grove Doppler Radar module (https://wiki.seeedstudio.com/Grove-Doppler-Radar/). The Grove powers up and has onboard LEDs showing it's functioning but I can't get serial.on('data' to fire on the Jolt.

I've got my code working from loopbackA to B, and checksums right, but when I move to the hardware pins I get nothing. I've been through all the Espruino troubleshooting guides, and setting the Grove to one side for a minute, I can't even get a single wire loopback test to work on the H0-7 pins of the Jolt, like this:

Serial1.setup(9600, {rx:serial_pin, tx:serial_pin});
Serial1.on('data', function (data) { print(" "+data); });
Serial1.print("Hello World");

[AndySmee]

I'm so fed up with trying that I'm struggling to cut and paste examples...

Serial1.setup(9600, {rx: H2, tx: H3}); Serial1.on('data', function (data) { console.log("<Serial> "+data); }); Serial1.write("Hello World");

Tried on Serial2 as well, and across H4/H5 pins

[AndySmee]

Made a breakthrough, I found I could get a wired loopback to work on the scl/sda on Q3. So now I have made contact with the Grove, powered on the common 5V on the main rail but sending and receiving data on the Q3 connector. That will do for now...

[AndySmee]

So, to recap, I still would prefer to use a serial on the high power ports of the Jolt but I have a working connection to the Grove Doppler Radar module as follows:
sensor = new Gdr(Serial2, Q3.scl, Q3.sda);
Where Gdr is:

function Gdr(serialPort, rxPin, txPin) {

   if (!(serialPort instanceof Serial)) {throw '"serialPort" parameter is not a serial port!';}

   if (!(rxPin instanceof Pin)) {throw '"rx" parameter is not a Pin!';}

   if (!(txPin instanceof Pin)) {throw '"tx" parameter is not a Pin!';}

   this.buffer = new Uint8Array(10);

   this.bufferIndex = 0;

   this.serial = serialPort;

   this.serial.setup(115200, {rx: rxPin, tx: txPin});

   console.log('connected',this.serial.isConnected(),rxPin,getPinMode(rxPin),txPin,getPinMode(txPin));

   this.serial.on('data', this.onSerial.bind(this));

}

Which reports as:

connected true D38 input D39 af_output

My next problem is that the baud rate of 115200 is leaving very little capacity for processing without causing "New interpreter error: UART_OVERFLOW" messages. The Grove seems to be very chatty, it never shuts up! It sends 4 bytes continuously just to say it's still there!

I've paired down the code which looks for the start byte but I still need to amass 10 bytes before parsing the message. I use a setTimeout when I hit 10 bytes to give the processor time to catch up before parsing, and then another setTimeout before displaying the message. The problem is, I was hoping to have this working inside another app which needs to do more compute. Is there anything I can do to offload the buffer checking to ignore unwanted serial data?

[gfwilliams]

Glad you're getting somewhere! the issue you have is that while the H0..7 pins will output digital signals (eg from the UART) the signals that come back in go through a potential divider so they can safely handle the higher voltage, so a 5v signal will get shifted down to level where it can't be used as a direct input to a peripheral that's expecting a digital signal.

The normal IO pins on the Quiic connectors will only accept 3.3v signals so it might be worth checking the Grove module isn't going past that.

Looking at the module it seems it can run off 3.3v, so you could just connect it completely to Q0 or Q1 (which each contain a FET on the ground wire that'd allow you to turn it on and off when needed?).

Shame about all the extra noise from the module. What about using this.serial.unsetup() to turn off the serial device when you don't want it so it's not getting any more characters? Either that or you could use .setup and just set the RX pin to a different pin that doesn't have anything on).

I don't know what you're doing in this.onSerial but it's possible there would be ways to speed that up. I'm happy to take a look if you post up the code

[AndySmee]

Thanks, I tried again using Q0 to power the Grove but it and the Jolt just flash light and then stop working, so I've reverted to the outside spec way of powering it. In the meantime, the Grove is disappointing for my use case as it won't detect such a small target which is not made of radar reflective material (a cricket ball)

[gfwilliams]

I tried again using Q0 to power the Grove but it and the Jolt just flash light and then stop working

Wow, ok - I guess maybe the module draws too much power when on. I've noticed with some things that even though they say they only draw some current (say 100mA) they have a bunch of big capacitors which draw an awful lot of power when first powered on.

Did you manage to check the voltage on the serial line and see if it was just 3.3v so you could stick it straight into the Quiic connector on the Jolt?

[AndySmee]

I saw something suggesting 300mA power draw but, to be honest, I've moved away from using the module because it doesn't acquire my chosen moving object, a cricket ball! It has a resolution within a 10m range which seems to be humans, cars and possibly smaller radar-reflective objects, but I suspect a cat or dog is the smallest meaningful moving object it is useful for, not soft materials and flying objects.

As an aside, for those looking for similar use cases, I noted that golf swing radar detectors are always placed where the club head will pass the sensor, and it is not the ball's speed being measured at all. I do have an inkling that a radar horn antenna might turn that module into a radar gun, but that's for another day.