I'd like to use a nRF52840's UARTE0 as interface for a DMX512 controler.
For that I'd need to set the interface at 250000 baud with 8N2. But I can't see how to configure 2 stop bits via nrf_uarte_configure(). This function allows to control HWFC and parity but not the number of stop bits, why?
What can I use instead?
In addition the DMX512 protocol would require a break (~100µs LOW, ~12µs HIGH) as lead-in for the following data train (up to 513 bytes).
Thanks for the reply.
In my topic title and text I do refer to UARTE/UARTE0 (using EasyDMA) and the docs do suggest HW support for 2 stop bits here
Hence I was surprised not to find that the function - apparently targeting the EasyDMA enabled UARTEx interfaces (going by the name nrf_uarte_config() - note the E) - would not allow for that bit to be controled.
Thanks for the tip about disabling the interface temporarily.
This works (code written in C++ based Particle.io Wiring dialect)
uint8_t * const pBase = (uint8_t *)0x40002000; // UARTE0 (UARTE1 .. 0x40028000) (doc. 6.34.9)
uint32_t* const pStartTX = (uint32_t*)&pBase[0x008]; // TASKS_STARTTX write 1 to initiate
uint32_t* const pStopTX = (uint32_t*)&pBase[0x00C]; // TASKS_STARTTX write 1 to initiate
uint32_t* const pEnable = (uint32_t*)&pBase[0x500]; // ENABLE register (doc. 6.34.9.6 Enable .. 8, Disable .. 0)
uint32_t* const pConfig = (uint32_t*)&pBase[0x56C]; // CONFIG register (doc. 6.34.9.18)
void breakTx(uint32_t duration = 100) {
*pEnable = 0;
pinResetFast(TX);
delayMicroseconds(duration);
*pEnable = 8; // enabling takes ~14µs which should work as DMX512 ABM (~12µs)
}