Send UART break

[endian-benjamin]

Our nRF52840 is connected via UARTE @ UART_1 to a modem which does not have a WAKE pin - the only method of waking it from sleep is to send a UART break. Is there any way to accomplish this on the nRF52840?

[Edvin]

Hello,

I am not sure exactly what sort of device that is, but it looks like from here, that a break is the line being held low.

You can try to send a UART string containing 0x00's, and see if that triggers the modem to wake up.

If not, a UART break condition is just the line held low, so you can try to disable the UART, set the pin as an output, put it in logic low (set it to 0. You can use nrf_gpio_pin_clear(pin_number)).

But first, try to send a string containing some 0x00's.

Best regards,

Edvin

Best regards,

Edvin

[awneil]

Sending 0x00 at the correct baud rate should not be interpreted as a Break - because of the Start & Stop bits.

But Turbo J's suggestion to use a way-too-low baud rate is a good one - unless this mystery "modem" is already running at a very slow speed ...