Reading Battery and RP voltage from Nybble v0.2

A0 on Arduino can only accept 5V as max input. The output value should be 1024. There is a voltage divider for A0 so that it can be attached to the battery. So the readings (650 or 300) are relative, not absolute voltages. On V0_2, the reading is about 1/3 of the battery voltage. So 300/1024x5x3=4.5V. That’s lowVoltageThreshold/maxOutput x maxInput x dividerFacotor. It means that when the battery’s voltage is lower than 4.5V, the low voltage warning will be triggered.

Thanks Rongzhong,

I set the low voltage 'meow' warning to 6.5v, (2 * 3.2v min Li Ion level) by changing the 300 to 450

I have also created a new command to read the voltage dirrectly from the Nybble_v0.2 board.

in Nybble.ino at line561 after the

case 'a': {

PTLF("abort calibration");

for (byte i = 0; i < DOF; i++) {

servoCalibs[i] = servoCalib( i);

}

break;

}

I inserted:

        case 'v': {
            float voltage = analogRead(BATT);
            Serial.println(voltage/1024 * 5 * 3);
            break;
          }

Additionally,

So I could get access to the voltage while Nybble is operating, I updated the Flask API code https://github.com/leukipp/OpenCatWeb with the two following updates:

Update 1: in app.py after line 154, @app.route('/api/status/j/')

def api_status_j():

return jsonify({'status': {'j': serial.write(SerialCommand('j'))}})

I inserted:

@app.route('/api/status/v/')
def api_status_v(): 
    return jsonify({'status': {'v': serial.write(SerialCommand('v'))}}) 

Update 2: in bus.py after line 33,

if '\t' in line:

print(line)

return line.split('\t')

I inserted:

 if '.' in line:
     print(line)
     return line

Works like a treat. Meows when the voltage is getting low, and I can use the web API to measure the voltage usage as Nybble bounds around.

D L

Out of pure interest I grabbed the standard Firmata sketch https://github.com/firmata/arduino/blob/master/examples/StandardFirmata/StandardFirmata.ino and compiled it to get an indication of how big it was.

Sketch uses 12492 bytes (40%) of program storage space. Maximum is 30720 bytes.
Global variables use 1053 bytes (51%) of dynamic memory, leaving 995 bytes for local variables. Maximum is 2048 bytes.

My Nybble.ino (v0.2 plus the extra lines to implement voltage) uses the following:

Sketch uses 30396 bytes (98%) of program storage space. Maximum is 30720 bytes.
Global variables use 1195 bytes (58%) of dynamic memory, leaving 853 bytes for local variables. Maximum is 2048 bytes.

Need a bigger boat!

D L