Serial1 on IND.I/O

Eventually, I need to be able to use modbus to communicate with another device. I connected everything and it didn't work, so I've been simplifying and simplifying, and I'm down to this:

I am trying to get my IND.I/O to use its Serial1 (RS-485) port. Here is my sketch:

void setup() {
  Serial1.begin(9600, SERIAL_8N2);
  pinMode(9 /*TxEnablePin*/, OUTPUT);
  digitalWrite(9 /*TxEnablePin*/, LOW);
  delay(1);
}

void loop() {
  digitalWrite(9, HIGH);
  Serial1.write(85);
  delay(200);
  digitalWrite(9, LOW);
  delay(200);
}

I put a scope on the A and B RS-485 lines. With this sketch, I see this in the scope: https://imgur.com/SztEalF.png. As far as I can tell, this is basically what the simple modbus master library does (albeit grossly simplified).

It looks like the writes to pin 9 are simply setting the serial output to high or low!? (and the other wire is negative of the main wire.) When I change the delays, the length of time high or low (depending on which delay I change) changes accordingly.

If I change the code to use the Indio library like so:

#include <Indio.h>

void setup() {
  Serial1.begin(9600, SERIAL_8N2);
  Indio.digitalMode(9 /*TxEnablePin*/, OUTPUT);
  Indio.digitalWrite(9 /*TxEnablePin*/, LOW);
  delay(1);
}

void loop() {
  Indio.digitalWrite(9, HIGH);
  Serial1.write(85);
  delay(200);
  Indio.digitalWrite(9, LOW);
  delay(200);
}

I get the following on the scope: https://imgur.com/f3iVsDn.png. So apparently digitalWrite(9, HIGH) is different from Indio.digitalWrite(9, HIGH). That's fine, at least I don't get 400 ms pulses, but I would really like to see my "85" be serialized on the line!

Please let me know what I should do next to try to troubleshoot this issue. Have I missed some configuration? Is there another test I should be running to rule out other problems? Thanks!

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Aaron

Aaron

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Asked on 7/30/20, 4:11 PM

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