nRF52840 Dev Kit UART Example uses default 115200 baud on low-speed <10kHz pins?

[tb32]

The nRF52840 UART example uses pins 1.13 and 1.14 for the TX and RX pins on the Dev Kit (uart_pca10056) and has a default baud rate of 115200, but the 1.13 and 1.14 pins are specified as low speed only. Is this a mistake in the example or the datasheet?

[Simonr]

Hi

I'm sorry, but in what SDK version are you seeing this? I double-checked the uart_pca10056 example in SDK v.17.0.0 to make sure, and there the RX_PIN_NUMBER and TX_PIN_NUMBER pins are set to P0.08 and P0.06 by default. Either way, using low-frequency pins for high-speed operations are only a problem if you're using the radio as well, as these pins are located near the radio, and may interfere. They shouldn't cause any other problems with your application.

Best regards,

Simon

[tb32]

Hi Simonr,

I'm also looking at v.17.0.0 but I was looking at SER_APP_RX_PIN/SER_APP_TX_PIN and SER_CON_RX_PIN/SER_CON_TX_PIN. In the connectivity example here pins 1.13 and 1.14 are used for TX and RX. The example project has a default of 115.2Kbaud in the sdk_config file. As mentioned on that page: "The SDK provides a sample serialization setup consisting of two nRF5 Development boards. One of these boards serves as application board and hosts the actual Bluetooth or ANT application. The other board serves as connectivity board and supplies the radio connection." So it seems as though that example uses low speed pins at greater than 10kHz on a board that uses a radio.

[Simonr]

Hi

You're absolutely correct. I would suggest editing this example to use some other GPIOs for UART connectivity in order to avoid any performance degradation. I will report this internally, so this might be fixed in a future release. Thank you for sharing your discovery with us!

Best regards,

Simon