RE: Starting from the beginning with UART

Simon — Mon, 01 Apr 2019 08:38:53 GMT

I am happy to help, and I am glad I made you wiser. Please ask if you have any more questions.

Best regards,

Simon

RE: Starting from the beginning with UART

Koenigs — Fri, 29 Mar 2019 01:53:30 GMT

Sorry for the very late reply, I haven't had time to come back on this for a long while. Just found a bit of time only very recently.

Thanks for this awesome answer, as a beginner this is exactly the kind of information I was looking for.

I know UART seems to be a basic knowledge for experienced developer so I appreciate you took the time to explain it to me and the difference with the Nordic UART Service.

It's much clearer to me now.

Thanks again!

RE: Starting from the beginning with UART

Simon — Mon, 17 Dec 2018 16:57:32 GMT

I would start by making a distinction between UART and NUS (Nordic UART Service). UART is a physical circuit, which main purpose is to send and receive messages between two devices. Transmitted messages goes out of the TX pin and incoming messages goes into the RX pin. NUS is a proprietary BLE Service, its structure is similar as the UART, as it includes the two characterstics TX and RX. A message is transmitted from the application (server) implementing the service by notifying the value in the TX char, in which the peer (client) will receive. A peer can write to the RX char., and the application will receive the message.

Both NUS and UART consists of two “channels” TX and RX, and enables simple communications between two devices.

It is quite easy to “bridge” communication over UART, to communication over BLE NUS, due to their similar structure.

The ble_app_uart peripheral example, implements the the NUS Service, and allows you to connect and communicate to a client. The client can be another nRF5x device (with the ble_app_uart central example) or a phone. The application will “convert” the messages written into the RX char. and send it over UART, and notify a value change of the TX char. to the client, when it receives messages over UART. The image below illustrates the communication flow if you connect the application to a computer through UART.

*"Service" should be "server"

There exist many other possibilities:

phone←(BLE) →device←(UART)→computer
computer←(UART) →device←(BLE) →device←(UART) →computer
device←(BLE)→device
device←(BLE)→phone
It is also possible to communicate one-to-many, by exploiting the possibilities of the nRF52 of maintaining several links simultaneously

NUS/UART can be useful if your application requires wireless low energy communication between two or many devices and if you would like an UART interface to your computer. The communication throughput and range are of course restricted by BLE.