Can nRF52840 support UART buad rate 921600/1000000 correctly?

[Alan]

Hi 

Can nRF52840 PDK support UART buad rate 921600/1000000 correctly?

I am testing UART with below example for our product development:

nRF5_SDK_14.2.0_17b948a\examples\peripheral\uart

If buad rate is 115200~460800, the putty / realterm can see the correct loopback string from J-LINK CDC UART port.

However, the loopback string cannot parse correctly in putty / realterm with buad rate 921600 / 1000000.

All I just modify the buad rate from NRF_UART_BAUDRATE_115200 to NRF_UART_BAUDRATE_921600 / NRF_UART_BAUDRATE_1000000.

It should be work, is there any limitation about J-LINK CDC UART?

Thanks.

Alan

[Nguyen Hoan Hoang]

JLink cannot handle that baudrate.  Try it with a FTDI breakout instead.

[Alan]

Hi Nguyen

Thanks.

I double checked the PDK document - nRF52840_PDK_User_Guide_v1.1.pdf

Although it said that "Flexible baud rate setting up to 1 Mbps." (1Mbps = 1000000?)

But "Baud rate 921 600 is not supported through the virtual COM port" on the page 11.

So the first description is quite misleading...

Alan

[Nguyen Hoan Hoang]

The nRF52 physical UART can support up to 1MBaud.  CDC com port is virtual so it only limited by your firmware.  You can support any baudrate you want.  THe baudrate limitation is also depends on the terminal software your are using.  I use CoolTerm.  By defaut, it is limited to 250K but you can enable any not listed baudrate by listing it in the baudrate.ini file.  It works much better at high baurate than PUTTY.