Nrf52840 UART device compatibility

[ephimee]

I have 3 devices that can communicate via UART:
1) nRF52840-DK (PCA10056)
2) FTDI (set to 5v logic)
3) BLE HM-19

I'm using the example in ./nRF5_SDK_16/nRF5SDK160098a08e2/examples/peripheral/serial_uartes

If I connect the FTDI to the NRF, I'm able to send and receive data.
ftdi.5v to nrf.5v
ftdi.gnd to nrf.gnd
ftdi.rx to P0.27
ftdi.tx to P0.26

If I connect the FTDI to the HM-19, I'm able to send and receive data.
ftdi.5v to hm.5v
ftdi.gnd to hm.gnd
ftdi.rx to hm.tx
ftdi.tx to hm.rx

But if I connect the NRF to the HM-19, it doesn't work.
hm.5v to nrf.5v
hm.gnd to nrf.gnd
hm.rx to P0.27
hm.tx to P0.26

I have set the baudrate to 9600 on every device.

I tried swapping RX, TX.
I also tried first connecting RX,TX followed by power. Also the other way around power first and then connect RX, TX.

This is how I configure the uart:

NRF_SERIAL_DRV_UART_CONFIG_DEF(m_uarte0_drv_config,
                      ARDUINO_SDA_PIN, ARDUINO_SCL_PIN,
                      RTS_PIN_NUMBER, CTS_PIN_NUMBER,
                      NRF_UART_HWFC_DISABLED, NRF_UART_PARITY_EXCLUDED,
                      NRF_UART_BAUDRATE_9600,
                      UART_DEFAULT_CONFIG_IRQ_PRIORITY);

[Simonr]

Hi Philip

That might be the case, but it is strange that the communication works with the FTDI if there are any software issues on the nRF side. You can try using the regular UART example
\<SDK-FOLDER>\examples\peripheral\uart to communicate between the HM-19 and the nRF as well, as that is a very straight forward example that should make it work. Remember to set the baud rate to 9600 if that's what you want though, as the SDK examples are set to 115200 by default.

Are you able to provide the datasheet for your HM-19 so I can take a look at it? I haven't been able to find the datasheet for the correct one I think.

Best regards,

Simon

[ephimee]

I tried the example, but I don't get any output in the output window?

I don't have a datasheet for the HM-19