Need help using teensy 4.0 to emulate a serial remote control

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bxaxp

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I am new to teensy and microcontrollers in general, and I'm hoping to get some help here. I am trying to use my teensy 4.0 to control a device (audio DSP) via the UART based remote port and I'm a little stuck. I can sniff the communication between the device and the remote just fine using the teensy. When a message is sent from the remote, the device responds, and I have mostly decoded the messages that I care about. The problem is that when I send exactly the same messages to the device, it either sends no response, or a response that does not match the response that the remote gets. When I read the sent messages from another serial port on the teensy, they look exactly the same. There are some handshake messages that are sent to the device when the remote is first plugged in, and I don't get the same responses from those either.

I am mostly just wanting to control the volume of the device, and the interesting thing is that most of the time, the DSP accepts the volume messages that I send through the teensy, even though it doesn't send a response, but it does not work 100% of the time. What could be going on here? I played around with the baud rate a little bit to no avail.
 
Does the 'device' have a spec showing the command language? Perhaps it is missing a terminator char or something simple.

Sounds like it would be a good case for a logic analyzer to monitor the full context and extent of the transfers.
 
I could not find any specs. I had to use a logic analyzer to figure out the protocol and baud. I could probably read the teensy data in the logic analyzer and compare side by side, see what the differences are. I will give that a try.
 
The logic analyzer did reveal the difference. Turns out that there are 2 stop bits vs 1. I wish I had thought to check that before posting. Thanks for your help.
 
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