UART Port baud rate

Support
1

Hi all,

I was wondering if anyone had experimented with the baud rate of the ODrive serial port. Currently it defaults at 115200 as indicated in Board/v3/Src/usart.cpp .

Is it possible/safe to change this value?

Thanks

2

I know @je310 did this.

@je310 do you mind sharing what you changed?
Thanks

3

Jelsdon == je310 (lost my password it seems). Yes:
Firmware/Board/v3/Src/usart.c
Line:
huart4.Init.BaudRate = 115200;
Can be changed. Though there are some limitations on what is allowed. I have used 921600 to great success, which is fast enough for me to get the update frequencies I want. I tried 2500000, which does not work. You can check using the CubeMX tool, as it does reject the settings that are too high (presumably based on various clocks, which I would not change unless you understand how they affect the rest of the ODrive)

4 Likes
4

Thanks @Jelsdon, a rate of around 921600 would be ideal for my needs. Glad to hear it is so easy to change!

5

Just to add that today I’ve successfully tested odrive at 2000000 baud together with a Teensy 3.5. 1000000 baud works as well.

6

In case it’s usefull for anyone

today I tried to

  • change the value of Firmware/Board/v3/Src/usart.c / huart4.Init.BaudRate = 115200;
  • reflash odrive with new elf file
  • then change my odrive <-> arduino UART baudrate in arduino code accordingly
  • then read odrive firmware value through UART from arduino

=> to no avail. :confused:

These are my observations
Serial1.begin(115200); // ok. just works
// Serial1.begin(921600); // fails. no communication at all
// Serial1.begin(460800); // fails. no communication at all
// Serial1.begin(230400); // fails. cryptic communication. homing works but streaming positions is a disaster (collisions with main chassis)

maybe i did something wrong.
maybe i should try with a teesy 3.5 board.
Dunno.

i’m stuck with 115200 for now. too bad this is not dynamically configurable through odrivetool like the other parameters.

7

Just to point out that in my case the comm wires were quite short, i.e. <20cm. With this setup I was able to reliably use 921600 and 1000000 baud using a teensy 3.5. 2000000 also seemed to work, but there were some reliability issues

8

Thanks for pointing out the cable length. I used two wires, not twisted together. No ferrite.
Just like yconst the arduino sits immediately next to the odrive board, in the 15cm range (did not precisely measure)

9

Were you using software serial or hardware uart on the arduino? The max speed arduino uno can handle on software serial is about 115200.

10

Exclusively hardware tx/rx
I’l not in front of it but I believe in the arduino méga code, it was ‘Serial1’