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Firmata firmware for Arduino
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Extra preceding bit is always sent to HardwareSerial (Serial1, Serial2, Serial3) #302

Open thorikawa opened 8 years ago

thorikawa commented 8 years ago

When I use StandardFirmata on Arduino Due and connect it with a serial servo motor with Serial1 on pins 19 (RX) and 18 (TX), the servo motor does not work.

I found a issue that an extra preceding LOW bit is always sent here from setPinModeCallback function which is called from systemResetCallback function at the initial setup of the sketch. Call stack is as below.

at setPinModeCallback (https://github.com/firmata/arduino/blob/2.5.3/examples/StandardFirmata/StandardFirmata.ino#L292)
at systemResetCallback (https://github.com/firmata/arduino/blob/2.5.3/examples/StandardFirmata/StandardFirmata.ino#L724)
at setup (https://github.com/firmata/arduino/blob/2.5.3/examples/StandardFirmata/StandardFirmata.ino#L771)

The servo motor I am using is so sensitive that this extra bit prevent it from interpreting the serial command properly. When I change the condition line here from if (IS_PIN_DIGITAL(pin)) { to if (IS_PIN_DIGITAL(pin) && !IS_PIN_SERIAL(pin)) {, everything works well. So I am really sure this line is the cause of my issue.

Do we really need this digitalWrite(PIN_TO_DIGITAL(pin), LOW); line for all digital pins including hardware serial pins at the initial setup? If not, I can send the pull request to fix it as I mentioned above.

By the way, this issue might be related with #272 which is also an issue with Arduino Due and Hardware Serial 1.

soundanalogous commented 7 years ago

if (IS_PIN_DIGITAL(pin) && !IS_PIN_SERIAL(pin)) { would prevent setting the pinMode of any HW serial pins to OUTPUT if the UART is not used. This could be a common case for the Due or Mega since they each have 4 UARTs.

One approach could be:

if (Firmata.getPinMode(pin) == PIN_MODE_PWM) {
  // disable PWM
  digitalWrite(PIN_TO_DIGITAL(pin), LOW);
}

That way it's only called if changing a pin's mode from PWM to digital output.

soundanalogous commented 7 years ago

PR submitted but needs testing before it can be merged: https://github.com/firmata/arduino/pull/311.

soundanalogous commented 7 years ago

@thorikawa please checkout the issue-302 branch and report if it fixes your issue. There is a slight chance it still could be a problem due to the RX pin being set to OUTPUT, however this should correct that as long as it doesn't generate a state change on the pin.

thorikawa commented 7 years ago

@soundanalogous Thanks, I just tested against with the new branch, but did not work. I will dig into the issue more later.