RS485 Communication Data Changing Issue

Technical Support
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1

We are trying to communicate with an external device attached to SOM using ttyLP2 , and is communicated via rs485 using C program .But the data read from port is wrong and having extra data .

Sending Data: 1 3 0 0 0 1 132 10

Tx is data sending from VF61

Rx is data read on external device/ PC

12:24:10.718 [TX] - 01 03 00 00 00 01 84 0A

12:24:11.395 [RX on Other side] - 01 03 00 00 00 01 84 0D 0A

When examining in detail,its found that when data is ‘0A’ only this 13 (0D) is prefixed.

2

Hello @abhil

Could you provide the software version of your module? Which carrier board are you using?

What is your application and your use-case for RS485?

When examining in detail,its found that when data is ‘0A’ only this 13 (0D) is prefixed.

Why are you sending a 0x0A, since this is not printable character? Actually every value smaller than 31 (0X1F) is not a printable character.

Best regards,
Jaski

3

BSP Verison is Colibri_VF_LinuxImageV2.8b5. Also tried with Colibri_VF_LinuxImageV2.8b3.
Tried with Evaluation kit v3.1A

What is your application and your use-case for RS485? >> 485 is used for modbus protocol similar communication

Why are you sending a 0x0A, since this is not printable character? >> Actually its generated as crc byte.

4

Please note that both BSP 2.8b3 as well as 2.8b5 are no longer supported as they got superseded by BSP 2.8b6 meanwhile even having been declared stable.

5

Updated BSP 2.8b6 as per instruction from Toradex support. But still facing the same .
Since its a generated CRC byte we cannot expect when it occurs. So is there any solution to avoid this conversion.

6

hi @abhil, is this issue solved?

7

Sorry for delay. was busy with another task. Also
It seems working. Now able to get reply from otherside device.
I think 0A is not creating issue now after setting the mentioned option.

Thanks jaski

8

hi @abhil

This CRC conversion to 0xA cannot be avoided but you can avoid the translation newline to carriage return-newline, by setting the option:
[-]onlcr translate newline to carriage return-newline
as explained here.

9

Perfect that it works. Thanks for the feedback.