New boards are ready and are being tested. Here is one connected to a Bluetooth module charging a battery:
This is the code used in battery voltage and charge current monitoring:
float readVcc()
{
signed long resultVcc;
float resultVccFloat;
// Read 1.1V reference against AVcc
ADMUX = _BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
delay(10); // Wait for Vref to settle
ADCSRA |= _BV(ADSC); // Convert
while (bit_is_set(ADCSRA,ADSC));
resultVcc = ADCL;
resultVcc |= ADCH<<8;
resultVcc = 1126400L / resultVcc; // Back-calculate AVcc in mV
resultVccFloat = (float) resultVcc / 1000.0; // Convert to Float
return resultVccFloat;
}
const int current = A6;
const int lipo = A7;
float vout = 0.0;
float vin = 0.0;
int value = 0;
void setup()
{
Serial.begin(9600);
}
void loop()
{
float napetost = readVcc();
float tok = ((analogRead(current) * napetost / 1024 ) * 1200) / 3; // convert the ADC value of charge current to miliamps
float baterija = ( analogRead(lipo) * napetost / 1024 ) * 2; // measuring battery voltage
Serial.print("Vcc = ");
Serial.print(napetost);
Serial.println("V");
delay(400);
Serial.print("Charge current = ");
Serial.print(tok);
Serial.println("mA");
delay(400);
Serial.print("Battery voltage = ");
Serial.print(baterija);
Serial.println("V");
delay(400);
Serial.println("----------------------------");
delay(2000);
}
/*
Improving accuracy:
To do so, simply measure your Vcc with a voltmeter and with our readVcc() function. Then, replace the constant 1107035L with a new constant:
scale_constant = internal1.1Ref * 1024 * 1000
where
internal1.1Ref = 1,1 * Vcc1 (per voltmeter) / Vcc2 (per readVcc() function)
Example:
For instance, I measure 3,43V from my FTDI, the calculated value of Vref is 1,081V.
So (1,081 x 1000 x 1024) = 1107034,95 or 1107035L rounded up.
Use smoothing example from IDE to smooth the data from ADC.
*/
Charge current is limited to 400mA and can be easily changed to another value by changing just one resistor.
