Connecting Jetson TX2 to MDC2460

[Tyagi]

Hi,

I am trying to connect my Jetson TX2 to Roboteq MDC 2460 using my rs232 connection. I was able to make the connection work through the usb b port and the roboteq linux api. I am not able to connect and control it using the uart control as it is not detecting it. I used the Jetson’s J17 serial connection and connected the rx,tx, and gnd accordingly with the rs232 output of the motor controller. Have you guys faced this issue before? Do you have a solution? is there any code available that I can grab to get started.

Best regards,
Tyagi

[SuperDroid]

Hey Tyagi,

I would stick to the USB interface if possible.

Otherwise, you’ll need to implement the circuit shown on page 152 of the RoboteQ user manual. The Jetson UART operates on 1.8V/3.3V TTL (assuming you’re using the dev kit) and will not work with RoboteQ’s RS232 without a conversion. Please note that this conversion will invert the signal. So the MDC2460 will need to be configured through Roborun+ accordingly.

With either method, the code shouldn’t change except for the serial port being opened on the Jetson side.

[Tyagi]

Hi,

Thanks for getting back. I am leaning towards using the USB as well. I read in a few forums to not use USB for actual runs so i am trying the rs232 route.

What do you mean by conversion? is it to step down the voltage from 5 to 3.3v or changing the input signals to include cts/rts?

If I do add the rs232-ttl adapter then will I need to connect the rts/cts along with the rx/tx connection to the Jetson? I think I can change the config using roborun+ the software was pretty intuitive.

I used pin 2 (Tx),3 (Rx),& 5 (GND) from the Roboteq motor controller and connected it to my Jetson’s J17 port pin 4 (Rx), pin 5 (Tx), and Pin1 (GND). This is similar to the arduino connection in the documentation except for the 4.7K resistor. I setserial baud rate to 115200 just to make sure.

Thanks a lot for the reply. Look forward to your response.

[SuperDroid]

RTS/CTS are not needed here. All you need is a 4.7K Ohm resistor and two shottky diodes as shown in the manual (page 152). This circuit is converting the +/-10V RS232 from the RoboteQ to 0-3.3V TTL that the Jetson operates on.

Refer to page 153 in the user manual for how to configure inverted RS232 on the RoboteQ. It has to be done through a simple console command.

Also, we have used the USB interface on the RoboteQ motor controllers for a number of robots without any issues.

[Tyagi]

Thanks for clarifying that. It makes sense!

I just got of the phone with Roboteq as well. Since the Jetson port is a ttl they told me that an off the shelf solution would be to get a breakout board: https://www.roboteq.com/index.php/roboteq-products-and-services/roboteq-accessories/339/26/cables-accessories/bob15-detail and connect it to the rs232-ttl: https://www.roboteq.com/index.php/component/virtuemart/372/rs232-ttl-adapter-detail?Itemid=1154. This is just for future reference for myself and anyone with the same problem.

I have decided to follow your advice and stick to the usb for this prototype.

Thanks a lot for all the help!

[Author]

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