Nrf51822 with Modbus(TTL to RS485)

RE: Nrf51822 with Modbus(TTL to RS485)

Nidhi — Thu, 05 Dec 2019 12:17:38 GMT

There was a voltage mismatch. The code is working. I commented on ENABLE_LOOPBACK_TEST because I don't need it. Also, RE&DE pins are enable pins for Modbus (TTL to RS485).

RE: Nrf51822 with Modbus(TTL to RS485)

Simonr — Thu, 05 Dec 2019 10:19:29 GMT

I took another look at your code, and noticed that #ifndef ENABLE_LOOPBACK_TEST is commented out in your main loop. What exactly is happening with your loopback test? Also, I noticed you say RE&DE->P0.19. What are RE and DE?

Any luck using a logic analyzer to see what's going on on the UART lines? Also, what are you supplying the Modbus with? If this is 5V as well, there might be a voltage mismatch that occurs and causes this to happen.

Best regards,

Simon

RE: Nrf51822 with Modbus(TTL to RS485)

Nidhi — Thu, 05 Dec 2019 08:32:53 GMT

The problem is between Modbus(TTL to RS485) and NRF51. NRF doesn't get a response.

RE: Nrf51822 with Modbus(TTL to RS485)

Simonr — Tue, 03 Dec 2019 14:05:59 GMT

Just to confirm, the issue occurs somewhere between the computer and the nRF51, correct? Do you have a logic analyzer available that you can use in order to get a scope of the communication? That should be able to tell us where exactly the issue occurs, as I'm not sure in which part of the communication the error occurs.

Best regards,

Simon

RE: Nrf51822 with Modbus(TTL to RS485)

Nidhi — Tue, 03 Dec 2019 11:10:08 GMT

I connected PC toNRF51 to TTL to RS485(shown in the picture above) and further it to USB to RS485 converter and back to PC.

PC-> NRF51->TTL to RS485->USB to RS485 ->PC

using above code and connections.

Data is transmitted and can be seen on PC but can not be received back.

RE: Nrf51822 with Modbus(TTL to RS485)

Simonr — Tue, 03 Dec 2019 10:16:16 GMT

How did you test that the USB to TTL worked? Are you able to make the nRF51 and RS485 communicate if you don't transmit hex code? The RTS and CTS lines will be necessary if you're using hardware flow control in the UART communication.

Please add any further information that might help to narrow down the cause of this issue.

Best regards,

Simon

RE: Nrf51822 with Modbus(TTL to RS485)

Nidhi — Tue, 03 Dec 2019 08:47:19 GMT

I tried the UART example with USB to TTL and its working fine.

Connections as per I have written are correct, I don't know if I need to connect RTS and CTS. The problem is NRF51 is not communicating with RS485, I am sending hex code but not getting a reply. I am pretty sure I am not messing connections.

RE: Nrf51822 with Modbus(TTL to RS485)

Simonr — Tue, 03 Dec 2019 08:00:18 GMT

Can you try describing your issue in more detail? Please make sure that the TX and RX pins are connected correctly to both devices. If you're not sure about your connections, please share your hardware setup (schematics and a high-res picture of your setup) and I will take a look.

I suggest you try to get it working with our UART example before making any changes to the code. Just to see that you're able to get it running.

Best regards,

Simon

RE: Nrf51822 with Modbus(TTL to RS485)

Nidhi — Mon, 02 Dec 2019 18:43:22 GMT

Tried, only 3.3V supply...not working.

RE: Nrf51822 with Modbus(TTL to RS485)

Simonr — Mon, 02 Dec 2019 12:44:11 GMT

Please note that according to the nRF51822 product specification, the nRF51822 will not accept more than 3.6V. Please try reducing the voltage to 3.6V or lower, and see what happens.

Best regards,

Simon