# DMX on UART 0 / vs UART1

**URL:** <https://wled.discourse.group/t/dmx-on-uart-0-vs-uart1/3664>\
**Category:** Questions\
**Created:** [September 29, 2021, 8:15pm UTC](https://wled.discourse.group/t/dmx-on-uart-0-vs-uart1/3664 "2021-09-29T20:15:38Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![andorian](https://avatars.discourse-cdn.com/v4/letter/a/46a35a/32.png) [@andorian](https://wled.discourse.group/u/andorian)\
**Post date:** [September 29, 2021, 8:15pm UTC](https://wled.discourse.group/t/dmx-on-uart-0-vs-uart1/3664/1 "2021-09-29T20:15:38Z")

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I am quite new to the ESP8266 so maybe somebody an shine a light. I am trying to get DMS output working on a H803 module, which has the DMX TX pin on ESP U0TXD (GPIO1)

I configured the DMA output pin to 1 and observed it on a scope. I see 1.3ms pulses with an interval of approx. 28ms. Every 15 pulses some of them look more like data, but nothing looks like the 4us bit time of DMX. I wondered if it is possible that DMX uses UART1 while I am using a UART0 pin.

When looking into the DMA code I find the baudrate being set to ‘serial1’ which a is HardwareSerial instance. Hardware serial expects the UART number in the constrcutor, but I cannot find where this is done.

Anyone who can clarify the DMX serial vs UART for me ?

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**Author:** ![andorian](https://avatars.discourse-cdn.com/v4/letter/a/46a35a/32.png) [@andorian](https://wled.discourse.group/u/andorian)\
**Post date:** [October 2, 2021, 6:52pm UTC](https://wled.discourse.group/t/dmx-on-uart-0-vs-uart1/3664/2 "2021-10-02T18:52:35Z")

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I can answer my own question here. For some reason VS code showed the text “software uart” when hovering over “Serial” (without the 1), so I did not expect this to be Hardware UART0.  
After some digging I found information that just “Serial” maps to UART0, so changed the code and now the DMX data was output to the correct UART for the H803WF module.