nrf7002-DK - Proprietary protocol - UART RTU framing

[iotdeveloper]

Hello,

I need to detect the end of messages coming through UART. nRF7002 asks requests and the device connected via UART responds. Baudrate is set to: 921600.

It is a proprietary protocol similar to MODBUS, where 2 bytes are be used to determine the length of the message.  The end of the message should be detected by a space between characters (3.5 characters) as described here:

Modbus Protocol

I would like to ask how to detect the end of frames on the nRF7002-DK?  Please ideally in the form of a procedure or piece of code.

Thank you

[Hieu]

Hi iotdeveloper,

The nRF7002 doesn't provide UART capability, so you would be actually using a different Nordic SoC here. On the nRF7002-DK, that would be the nRF5340.

There is a Modbus implementation in Zephyr that you can reference. It looks like their strategy for baud rate higher than 38400 is to simply delay for more than 3.5 character times. Refer: https://github.com/nrfconnect/sdk-zephyr/blob/ncs-v3.1.0/subsys/modbus/modbus_serial.c#L585-L590.

At the baud rate as high as 921600, if you want to optimize performance, you will have to use DPPI to connect UARTE and TIMER tasks and events.

Hieu