UART TASKS_SUSPEND and sending a break

[Moloch]

Hello everybody,

I have a few questions about the built-in UART (UART0) in the nRF51822.

1. I've noticed some registers that aren't fully documented in nrf51.h of the sdk. I'd like to know what TASKS_SUSPEND does. I'm also curious about SHORTS and if there's anything to know about POWER.

2. The UART can interrupt on a break (en.wikipedia.org/.../transmitter, which is great for my application (two UARTs, one on each chip, go to sleep as often as possible and wake each other with a break). Does the UART have the capability to send a break using a simple command, or must I bit-bang a break of the pin by switching the crossbar to GPIO?

Thank you!

[John]

You can generate a break on UART0 by disconnecting the UART transmit from the GPIO pin and setting the GPIO pin low for the amount of time required to generate a break. You can then reconnect the UART transmit to your GPIO pin and begin your transmission.

Here is how I did it for out project:

// First disconnect the transmit pin from the UART by 
// writing -1 to the PSELTXD register
NRF_UART0->PSELTXD = 0xFFFFFFFF;

// Set pin low to generate the necessary zeros on the line
nrf_gpio_pin_write(TX_PIN_NUMBER, 0);

// Delay for enough time to generate a break
nrf_delay_us(100);

// Reconnect the pin to the UART
NRF_UART0->PSELTXD = TX_PIN_NUMBER;