BMD 300 Baud rate

[DanielJack]

I am running a NUS at 115200 Baud and it works fine but when I run it at 921600 my BMD 300 triggers a Serial Fault.   Is there a trick to get the 921600 to work without flow control.

[Jørgen Holmefjord]

Hi,

The app_uart library used by ble_app_uart can only receie a single byte at a time, causing lots of interrupts for the CPU to update the buffer to receive more bytes. This limits the effective throughput and will give overflow errors on high baudrate/throughput without HWFC.

The Libuarte - advanced UARTE driver was created specifically to resolve this issue, using multiple larger buffers together with timers and PPI to handle switching and timeouts. If you replace app_uart with libUARTE, you should be able to use the higher baudrate.

Here is a good starting point for you!

Best regards,
Jørgen

[Jørgen Holmefjord]

DanielJack said:

Is there an example of this using the BMD 300?

No, there are normally no examples in the SDK for specific modules. Since the module is based on a nRF52832 chip, you should be able to use the PCA10040 project with only small modifications (GPIOs, crystals, etc).

[DanielJack]

How about a Keil based project?

[Jørgen Holmefjord]

You can copy the Keil project from ble_app_uart, there is just a few files you need to add to the project:

+ <file file_name="../../../../../../components/libraries/libuarte/nrf_libuarte_async.c" />
+ <file file_name="../../../../../../components/libraries/libuarte/nrf_libuarte_drv.c" />
+ <file file_name="../../../../../../components/libraries/queue/nrf_queue.c" />
+ <file file_name="../../../../../../modules/nrfx/drivers/src/nrfx_rtc.c" />
+ <file file_name="../../../../../../modules/nrfx/drivers/src/nrfx_ppi.c" />
+ <file file_name="../../../../../../modules/nrfx/drivers/src/nrfx_timer.c" />

And one path:

../../../../../../components/libraries/libuarte;

[DanielJack]

Which sdk_config.h do I use?  There does not appear to be any libuarte configurations in the UART example.

[Jørgen Holmefjord]

You should use the sdk_config.h file from pca10040 directory in the ble_app_libuarte example.

Copy arm5_no_packs directory from ble_app_uart\pca10040\s132\ to ble_app_libUARTE\pca10040\s132\. Then all you need to do is to add the source files and paths to the Keil project.