Nordic nrf52DK and UART

[SamiL]

We are trying to interface Texas Instruments TMP144 using the UART in nrf52DK. We attach the sensor board to UART pins in nrf52DK put it seems that the transmitted data is just echoed in console. Do we have to configure the Interface MCU somehow, or should we look for software error in our UART code?

[Simonr]

Hi

I assume you're trying to use the P0.06 and P0.08 pins for UART transmission here? If so, the reason is likely because these by default run to the interface MCU on the board instead of the pin headers by default, and you need to cut solder bridges SB23 and SB25 to isolate them to the connector interface. (See nRF 52 DK user guide for reference: https://infocenter.nordicsemi.com/pdf/nRF52_DK_User_Guide_v3.x.x.pdf) If that's not it, please share some details on what pins you're trying to use for communication and how the two boards are connected exactly, as well as what you're trying to transmit between the two devices.

Best regards,

Simon

[SamiL]

Hi, before cutting the solder bridges, I dug a bit deeper with this issue.

We are trying to interface TI's TMP144 sensor using the nrf52DK. We had some pin issues, but I assume that the commands are now going to TMP144. However, we are bit stuck with the protocol. Texas Instruments gives following protocol for TMP144:

 

Essentially it is 8-bit data with start and stop bits. The stop bit is, I guess, handled automatically with Zephyr by setting the 

UART_CFG_STOP_BITS_1. However getting the start bit, I assume we would need to use 9-bit communication but this seems unsupported with nrf52832. When I try to set  UART_CFG_DATA_BITS_9, we get -134 as error code when configuring the UART. 

The question is, how we can send the 0x55 with the start and stop bit using Zephyr and nrf52832?

[Susheel Nuguru]

We do not support the start bit in the UART, It is only 8-bit communication with a stop bit.