nRF51822 UART maximum speed without flow control

RE: nRF51822 UART maximum speed without flow control

Nguyen Hoan Hoang — Thu, 17 Nov 2016 00:46:59 GMT

Yes I do, 1 MBaud streaming to PC over USB bridge. Don't expect it to work with the onboard Segger though. You can only get that performance either using FTDI chip or with the IDAP-Link. Demo code is can be found from this blog. There is a link on the blog to the source code and look for UartPrbsTest example. Project for nRF51 & nRF52 on transmit side with Python script on the receiving side.

RE: nRF51822 UART maximum speed without flow control

Mark Bianchi — Wed, 16 Nov 2016 19:36:18 GMT

I just changed the clock source to NRF_CLOCK_LFCLK_RC and I still have framing errors.

Previous to trying this test (clock set to LFCLK_Synth), I added some code that would try different values for the BAUDRATE register, effectively going from the something less than the ideal setting to something more, in steps. This still didn't help with baud rates above 115,200. When I tried this baud rate setting "sweep" with 115,200, I would see errors when the baud rate was set + or - a few percent from ideal.

So at this point, I am beginning to think that baud rates above 115,200 don't work correctly, unless someone has proof to the contrary.

RE: nRF51822 UART maximum speed without flow control

bjorn-spockeli — Tue, 15 Nov 2016 10:24:53 GMT

Ok, are you seeing the framing issues if you use the internal(RC) oscillator?

RE: nRF51822 UART maximum speed without flow control

Mark Bianchi — Sun, 06 Nov 2016 03:53:15 GMT

Because I only have an external 32MHz crystal in the circuit and using the internal LF oscillator is less accurate than deriving the LFCLK from the 32MHz crystal. I am running FreeRTOS and have noticed tick inaccuracy using the internal LF oscillator vs the 32MHz crystal.

RE: nRF51822 UART maximum speed without flow control

bjorn-spockeli — Fri, 04 Nov 2016 11:49:01 GMT

@mjbianchi: Is there a specific reason why you have set the clock source to NRF_CLOCK_LFCLK_Synth and not NRF_CLOCK_LFCLK_Xtal?

RE: nRF51822 UART maximum speed without flow control

Mark Bianchi — Thu, 27 Oct 2016 19:53:31 GMT

Correct. We are not using the SoftDevice (or BLE at all) - we are just trying to get high speed UART traffic.

RE: nRF51822 UART maximum speed without flow control

bjorn-spockeli — Thu, 27 Oct 2016 12:29:59 GMT

This is UART only right? You're not using the SoftDevice and are sending/receiving data over BLE while using the uart without flow control?

RE: nRF51822 UART maximum speed without flow control

Mark Bianchi — Thu, 27 Oct 2016 02:41:58 GMT

A FIFO is not the problem. On the first byte received at the higher baud rate, I see a framing error, and then on each successive byte. There seems to be something wrong (like maybe the baud rate in the UART hw is faster than the baud I am running at, even though I am using the enum/defines in the SDK for setting the BAUDRATE register.

RE: nRF51822 UART maximum speed without flow control

Nguyen Hoan Hoang — Thu, 27 Oct 2016 00:22:50 GMT

You'll need a big fifo to run at higher speed. 1MBaud can be acheived on UART but not over BLE.