RS485 with UART and MAX485 with Nano / TX2

Autonomous Machines Jetson & Embedded Systems Jetson Nano
1

Hi,

I am trying to use a stepper motor driver with UART and convert it with MAX485 chip. The driver needs RS485 two wire half-duplex.
For my script I am using Python3.
However I can’t get any type of connection to my driver. I think It is because of the connection to/from the MAX485 chip.
With python code I can’t even see a connected serial port.

import serial.tools.list_ports
print(list(serial.tools.list_ports.comports(include_links=True)))

Output: [ ] #no port detected

My schematic
NOTE: The expansion header is from Raspberry, because it was already in my library and nearly similar to the Nvidia Nano

Bildschirmfoto 2020-07-12 um 21.50.21
Bildschirmfoto 2020-07-12 um 21.50.211456×854 9.03 KB

Best Regards
Chris

2

I cannot answer your question, but have one observation. The UART output of a Jetson will be 3.3V, and I see the RS485 output is 5V. Does your MAX485 chip use 3.3V on pins 1 and 4? If not, then communications with that chip will fail. The pull up/down at the UART pins of the Jetson to 5V would not be correct.

Note that some module output pins will be 1.8V, and that 3.3V is a carrier board design. Alternate carrier boards could use 1.8V instead, but the same question would apply as to whether the MAX485 chip accepts that voltage level. You can verify actual level with an oscilloscope.

3

Yes you are right. Didn’t see that. I bought a MAX485 module and it needs 5V, so it isn’t compatible with my Nano.
Will buy a 3v3 compatible module and test it again.
For using RS485 with my TX2 I think I will need a level shifter to shift 1.8V to min. 3V3
Thank you, will follow, when the new module arrived.