I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

[tony55723]

Hi，

DMX512 protocol is USITT（United States Institute for Theater Technology）Prescribed agreement

I want to follow this agreement to design

============ DMX512 protocol：

Baud：250K

Break：88us

MAB：8us

============ Data frame contains：

Start：1 bit

Data：8 bit

Stop：2 bit

Parity：None

I know that this design will still have errors.

I hope to give me some help, the project is urgent, thanks

Another stop bit need 2 bit, is it necessary to operate directly with registers?

（But the SDK is full of library operations？）

[Jørgen Holmefjord]

Hi,

Only UARTE peripheral support two stop bits, and this is only supported on nRF52840 and nRF52810 ICs. Unfortunatelu, there seems to be no support for setting this in the drivers. 

You can set two stop bits by writing the register directly after initializing the UARTE peripheral:

NRF_UARTE0->CONFIG |= (UARTE_CONFIG_STOP_Two << UARTE_CONFIG_STOP_Pos);

The UARTE peripheral have EasyDMA support, meaning transfers can happen in the background while CPU is busy handling BLE/softdevice events. If you frequently need to handle UART events with strict timing requirements, this will not work together with the softdevice.

Best regards,
Jørgen

[Jørgen Holmefjord]

I'm not familiar with the protocol details of DMX, but if it have strict timing requirements, an external MCU might be a better solution.

[tony55723]

Hi , 

Thank you all ,  for answers and suggestions.

I will try first with nRF52810 , If it doesn't work, consider using external microcontroller.

My DMX code in the main function , whether the format is correct or not ,  Will cause a crash

（The phone can search for BLE before adding the code,  But after adding the code, it won't work.）

[tony55723]

The cause of the crash is the repeated call of uart_init()

But DMX512 need low voltage(Break) and high voltage(Make after break).

Another wrong place, before delay88us and delay8us

Pin number needs to be changed to 6（【nrf_gpio_pin_clear(13)】 and【 nrf_gpio_pin_set(12)】）

Screenshot error , i am sorry

[PM Bubblynet]

hi, i am exploring around this DMX to BT integration and found this question and wanted to check if there is any news? is it possible to use the nRF52832 directly or needs a microcontroller to be an interface between DMX and lets say UART to the nRF52832?

[Jørgen Holmefjord]

My comment from 4 months ago still stands. There is only one CPU core in the nRF52832. If using BLE, the softdevice will always have highest priority, the DMX protocol will have to wait, meaning that if there are strict timing requirements an external MCU might be better solution.

[awneil]

PM Bubblynet said:

if there is any news?

I don't think so - I think everything that's been said remains true.