Using T-Display v1.1 with DMX to LED shield

Components & Accessories LEDs
1

Hi there,

First time poster here, so appreciate your patience; I have bought a DMX to LED shield, and a different ESP32 board (a LilyGo T-Display v1.1); Ultimately, I only want to use the DMX side, none of the LED driving side.

So I have been through both schematics ( https://cdn.sparkfun.com/assets/c/1/c/c/d/SparkFun_ESP32_Thing_Plus_DMX_to_LED_Shield.pdf and https://kreier.github.io/t-display/TTGO_T-Display_schematics.pdf ), and hooked up the following lines:

HWHookup
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I took the example DMX Output Code, with nearly no alteration (just wrote some additional addresses, in order to drive more channels on a test DMX fixture I hooked up, and added the explicit pins for 485_RX (26) and 485_TX(27), and changed the used pin for 485_EN (25)):

/*
  Writes DMX data to channel 1

  By: Dryw Wade
  SparkFun Electronics
  Date: 10/3/2023
  License: GNU. See license file for more information but you can
  basically do whatever you want with this code.
  This example runs two servos and a number of LED's off of 5 DMX channels
  
  Feel like supporting open source hardware?
  Buy a board from SparkFun! https://www.sparkfun.com/products/15110
  
  Hardware Connections:
  Connect a Thing Plus board to the SparkFun DMX Shield, and connect a DMX XLR-3
  cable between the shield and another device that outputs DMX data. You can use
  a second board and shield running Example 2!
*/

// Inlcude DMX library
#include <SparkFunDMX.h>

// Create DMX object
SparkFunDMX dmx;

// Create serial port to be used for DMX interface. Exact implementation depends
// on platform, this example is for the ESP32
HardwareSerial dmxSerial(2);

// Enable pin for DMX shield (Free pin on Thing Plus or Feather pinout)
**uint8_t enPin = 25;**
**uint8_t rxP = 26;**
**uint8_t txP = 27;**

// Number of DMX channels, can be up tp 512
**uint16_t numChannels = 5;**

// Create a counter as example data
uint8_t counter = 0;

void setup()
{
    Serial.begin(115200);
    Serial.println("SparkFun DMX Example 1 - Output");

    // Begin DMX serial port
    dmxSerial.begin(DMX_BAUD, DMX_FORMAT**,rxP,txP);**

    // Begin DMX driver
    dmx.begin(dmxSerial, enPin, numChannels);

    // Set communicaiton direction, which can be changed on the fly as needed
    dmx.setComDir(DMX_WRITE_DIR);

    Serial.println("DMX initialized!");
}

void loop()
{
    // Write counter to channel 1
    dmx.writeByte(counter, 1);
**    dmx.writeByte(counter, 2);**
**    dmx.writeByte(counter, 3);**
**    dmx.writeByte(counter, 4);**
**    dmx.writeByte(counter, 5);**
    

    // Once all data has been written, update() must be called to actually send it
    dmx.update();

    Serial.print("DMX: sent value to channel 1 thru 5: ");
    Serial.println(counter);

    // Increment counter (overflows back to 0 after 255)
    counter++;

    // Slow down communication for this example
    delay(100);
}

I can compile and upload and execute the code, the serial monitor for UART0 works fine, and no errors are reported, but I don’t get any DMX output on the port (tested the fixture with another DMX controller and it works).

Arduino: 2.3.2
esp32 board def: 3.1.1
latest Sparkfun DMX library installed.

What am I doing wrong?

Thanks in advance for your help!

All the best,

Fzd

2

Your DMX shield uses an RS-485 transceiver (like the MAX485 or similar), which has a driver enable pin. The SparkFun DMX library likely expects HIGH to enable TX mode.

Try to set the pin HIGH in setup() explicitly :

pinMode(enPin, OUTPUT);
digitalWrite(enPin, HIGH);  // Ensure the transceiver is in TX mode
3

Actually, I was making a stupid rogue error - I did not marry my RX with TX and vice versa between mother and daughter board - after swapping these, it all seems to work hunkey dory! As much as this is a monument to my stupidity, this might help others in the same situation ;).

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