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Support custom DMX output value #4876

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5940087
Add support to custom DMX output value
mrv96 Aug 26, 2025
708c76c
Minor refactor: replace for break with MIN()
mrv96 Aug 26, 2025
b4d976d
Refactor: roll some unrolled settings prints
mrv96 Aug 28, 2025
a0ed79b
Refactor: put max channels per fixture in a define
mrv96 Sep 1, 2025
a6963f0
Fix DMXStartLED size and position (back-compat.)
mrv96 Sep 1, 2025
316ef24
Prevent random-like DMX values from settings
mrv96 Sep 1, 2025
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15 changes: 12 additions & 3 deletions wled00/cfg.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -751,11 +751,15 @@ bool deserializeConfig(JsonObject doc, bool fromFS) {
CJSON(DMXStartLED,dmx[F("start-led")]);

JsonArray dmx_fixmap = dmx[F("fixmap")];
for (int i = 0; i < dmx_fixmap.size(); i++) {
if (i > 14) break;
for (int i = 0; i < MIN(dmx_fixmap.size(), MAX_CHANNELS_PER_FIXTURE); i++) {
CJSON(DMXFixtureMap[i],dmx_fixmap[i]);
}

JsonArray dmx_chsval = dmx[F("chsval")];
for (int i = 0; i < MIN(dmx_chsval.size(), MAX_CHANNELS_PER_FIXTURE); i++) {
CJSON(DMXChannelsValue[i],dmx_chsval[i]);
}

CJSON(e131ProxyUniverse, dmx[F("e131proxy")]);
#endif

Expand Down Expand Up @@ -1253,10 +1257,15 @@ void serializeConfig(JsonObject root) {
dmx[F("start-led")] = DMXStartLED;

JsonArray dmx_fixmap = dmx.createNestedArray(F("fixmap"));
for (unsigned i = 0; i < 15; i++) {
for (unsigned i = 0; i < MAX_CHANNELS_PER_FIXTURE; i++) {
dmx_fixmap.add(DMXFixtureMap[i]);
}

JsonArray dmx_chsval = dmx.createNestedArray(F("chsval"));
for (unsigned i = 0; i < MAX_CHANNELS_PER_FIXTURE; i++) {
dmx_chsval.add(DMXChannelsValue[i]);
}

dmx[F("e131proxy")] = e131ProxyUniverse;
#endif

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4 changes: 4 additions & 0 deletions wled00/const.h
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Expand Up @@ -655,4 +655,8 @@ static_assert(WLED_MAX_BUSSES <= 32, "WLED_MAX_BUSSES exceeds hard limit");
#define IRAM_ATTR_YN IRAM_ATTR
#endif

#ifdef WLED_ENABLE_DMX
#define MAX_CHANNELS_PER_FIXTURE 15
#endif

#endif
23 changes: 18 additions & 5 deletions wled00/data/settings_dmx.htm
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Expand Up @@ -7,10 +7,20 @@
<script src="common.js" async type="text/javascript"></script>
<script>
function HW(){window.open("https://kno.wled.ge/interfaces/dmx-output/");}
function GCH(num) {
function GCH(num){
gId('dmxchannels').innerHTML += "";
for (i=0;i<num;i++) {
gId('dmxchannels').innerHTML += "<span id=CH" + (i+1) + "s >Channel " + (i+1) + ": <select name=CH" + (i+1) + " id=\"CH" + (i+1) + "\"><option value=0>Set to 0</option><option value=1>Red</option><option value=2>Green</option><option value=3>Blue</option><option value=4>White</option><option value=5>Shutter (Brightness)</option><option value=6>Set to 255</option></select></span><br />\n";
gId('dmxchannels').innerHTML += "<span id=CH" + (i+1) + "s >Channel " + (i+1) + ": <select name=CH" + (i+1) + " id=\"CH" + (i+1) + "\"><option value=0>Set to </option><option value=1>Red</option><option value=2>Green</option><option value=3>Blue</option><option value=4>White</option><option value=5>Shutter (Brightness)</option></select><input name=DV" + (i+1) + " id=\"DV" + (i+1) + "\" type=number min=0 max=255></span><br />\n";
}
for (i=0;i<num;i++) {
const dv = gId("DV" + (i+1));
gId("CH" + (i+1)).addEventListener("change", (event) => {
if (event.target.value == 0) {
dv.style.display = "inline";
} else {
dv.style.display = "none";
}
});
}
}
function mMap(){
Expand All @@ -22,14 +32,17 @@
gId("gapwarning").style.display="none";
}
for (i=0;i<15;i++) {
const ch = gId("CH" + (i+1));
if (i>=numCh) {
gId("CH"+(i+1) + "s").style.opacity = "0.5";
gId("CH"+(i+1)).disabled = true;

ch.disabled = true;
gId("DV"+(i+1)).disabled = true;
} else {
gId("CH"+(i+1) + "s").style.opacity = "1";
gId("CH"+(i+1)).disabled = false;
ch.disabled = false;
gId("DV"+(i+1)).disabled = false;
}
ch.dispatchEvent(new Event("change"));
}
}
function S(){
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7 changes: 2 additions & 5 deletions wled00/dmx_output.cpp
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Expand Up @@ -40,8 +40,8 @@ void handleDMXOutput()
for (int j = 0; j < DMXChannels; j++) {
int DMXAddr = DMXFixtureStart + j;
switch (DMXFixtureMap[j]) {
case 0: // Set this channel to 0. Good way to tell strobe- and fade-functions to fuck right off.
dmx.write(DMXAddr, 0);
case 0: // Set this channel to the selected value.
dmx.write(DMXAddr, DMXChannelsValue[j]);
break;
case 1: // Red
dmx.write(DMXAddr, calc_brightness ? (r * brightness) / 255 : r);
Expand All @@ -58,9 +58,6 @@ void handleDMXOutput()
case 5: // Shutter channel. Controls the brightness.
dmx.write(DMXAddr, brightness);
break;
case 6: // Sets this channel to 255. Like 0, but more wholesome.
dmx.write(DMXAddr, 255);
break;
Comment on lines -61 to -63
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What happens to people's existing config that were using case 6 - can we be backwards compatible?

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@mrv96 mrv96 Aug 31, 2025 •
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Already pointed out by coderabbitai. Should I implement the solution suggested by it?

Another possibility may be to add a default behaviour in the switch-case statement which could write 255 to DMX or something else.

Let me know your favorite option.

image

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This should be the last open point (included coderabbitai actionables). Let me know how to proceed.

}
}
}
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7 changes: 6 additions & 1 deletion wled00/set.cpp
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Expand Up @@ -640,11 +640,16 @@ void handleSettingsSet(AsyncWebServerRequest *request, byte subPage)
if (t>=0 && t < MAX_LEDS) {
DMXStartLED = t;
}
for (int i=0; i<15; i++) {
for (int i=0; i<MAX_CHANNELS_PER_FIXTURE; i++) {
String argname = "CH" + String((i+1));
t = request->arg(argname).toInt();
DMXFixtureMap[i] = t;
}
for (int i=0; i<MAX_CHANNELS_PER_FIXTURE; i++) {
String argname = "DV" + String((i+1));
t = request->arg(argname).toInt();
DMXChannelsValue[i] = constrain(t, 0, 255);
}
}
#endif

Expand Down
3 changes: 2 additions & 1 deletion wled00/wled.h
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Expand Up @@ -473,7 +473,8 @@ WLED_GLOBAL bool arlsForceMaxBri _INIT(false); // enable to f
WLED_GLOBAL uint16_t e131ProxyUniverse _INIT(0); // output this E1.31 (sACN) / ArtNet universe via MAX485 (0 = disabled)
// dmx CONFIG
WLED_GLOBAL byte DMXChannels _INIT(7); // number of channels per fixture
WLED_GLOBAL byte DMXFixtureMap[15] _INIT_N(({ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }));
WLED_GLOBAL byte DMXFixtureMap[MAX_CHANNELS_PER_FIXTURE] _INIT_N(({ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }));
WLED_GLOBAL byte DMXChannelsValue[MAX_CHANNELS_PER_FIXTURE] _INIT_N(({ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }));
// assigns the different channels to different functions. See wled21_dmx.ino for more information.
WLED_GLOBAL uint16_t DMXGap _INIT(10); // gap between the fixtures. makes addressing easier because you don't have to memorize odd numbers when climbing up onto a rig.
WLED_GLOBAL uint16_t DMXStart _INIT(10); // start address of the first fixture
Expand Down
15 changes: 9 additions & 6 deletions wled00/wled_eeprom.cpp
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Expand Up @@ -16,7 +16,7 @@

//eeprom Version code, enables default settings instead of 0 init on update
#define EEPVER 22
#define EEPSIZE 2560 //Maximum is 4096
#define EEPSIZE 2570 //Maximum is 4096
//0 -> old version, default
//1 -> 0.4p 1711272 and up
//2 -> 0.4p 1711302 and up
Expand Down Expand Up @@ -343,20 +343,23 @@ void loadSettingsFromEEPROM()
//1024-2047 reserved

#ifdef WLED_ENABLE_DMX
// DMX (2530 - 2549)2535
// DMX (2530 - 2566)2535,2552
DMXChannels = EEPROM.read(2530);
DMXGap = EEPROM.read(2531) + ((EEPROM.read(2532) << 8) & 0xFF00);
DMXStart = EEPROM.read(2533) + ((EEPROM.read(2534) << 8) & 0xFF00);

for (int i=0;i<15;i++) {
for (int i=0;i<MAX_CHANNELS_PER_FIXTURE;i++) {
DMXFixtureMap[i] = EEPROM.read(2535+i);
} //last used: 2549
DMXStartLED = EEPROM.read(2550);
DMXStartLED = EEPROM.read(2550) + ((EEPROM.read(2551) << 8) & 0xFF00);
for (int i=0;i<MAX_CHANNELS_PER_FIXTURE;i++) {
DMXChannelsValue[i] = EEPROM.read(2552+i);
} //last used: 2566
Comment on lines +351 to +357
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💡 Verification agent

🧩 Analysis chain

Fix legacy DMX EEPROM overlap and DV back-compat (clamp to 15; don’t read DV from EEPROM).

Reading DMXFixtureMap with MAX_CHANNELS_PER_FIXTURE can overrun the legacy 15-byte block (2535–2549) and hit DMXStartLED at 2550 when MAX_CHANNELS_PER_FIXTURE > 15. Also, legacy EEPROM has no DV bytes at 2552+, so reading DMXChannelsValue from 2552… yields garbage. Migrate code-6 (“Set to 255”) to DV=255 and init the rest; keep reading map only up to 15. Additionally, guard 16-bit DMXStartLED for older versions and clamp to LED count.

Apply:

-  for (int i=0;i<MAX_CHANNELS_PER_FIXTURE;i++) {
-    DMXFixtureMap[i] = EEPROM.read(2535+i);
-  } //last used: 2549
-  DMXStartLED = EEPROM.read(2550) + ((EEPROM.read(2551) << 8) & 0xFF00);
-  for (int i=0;i<MAX_CHANNELS_PER_FIXTURE;i++) {
-    DMXChannelsValue[i] = EEPROM.read(2552+i);
-  } //last used: 2566
+  // Legacy EEPROM stores exactly 15 fixture-map bytes at 2535..2549
+  constexpr uint8_t LEGACY_DMX_CHANS = 15;
+  const uint8_t n = (MAX_CHANNELS_PER_FIXTURE < LEGACY_DMX_CHANS) ? MAX_CHANNELS_PER_FIXTURE : LEGACY_DMX_CHANS;
+  for (uint8_t i = 0; i < n; i++) {
+    DMXFixtureMap[i] = EEPROM.read(2535 + i);
+  } // last used: 2549
+  for (uint8_t i = n; i < MAX_CHANNELS_PER_FIXTURE; i++) {
+    DMXFixtureMap[i] = 0; // init extras
+  }
+
+  // DMXStartLED: legacy is 8-bit at 2550; optional high byte at 2551 for newer layouts
+  uint16_t dmxStartLo = EEPROM.read(2550);
+  uint16_t dmxStartHi = (lastEEPROMversion > 21) ? EEPROM.read(2551) : 0;
+  DMXStartLED = (dmxStartHi << 8) | dmxStartLo;
+  if (DMXStartLED >= MAX_LEDS) DMXStartLED = (MAX_LEDS ? (MAX_LEDS - 1) : 0);
+
+  // Legacy has no DV bytes. Initialize and migrate legacy "Set to 255" (code 6) -> DV=255
+  for (uint8_t i = 0; i < MAX_CHANNELS_PER_FIXTURE; i++) {
+    if (DMXFixtureMap[i] == 6) {
+      DMXFixtureMap[i]   = 0;   // "Set to"
+      DMXChannelsValue[i]= 255; // DV
+    } else {
+      DMXChannelsValue[i]= 0;   // default DV
+    }
+  }

To verify clamping and no overlap:

🏁 Script executed:

#!/bin/bash
# MAX_CHANNELS_PER_FIXTURE actual value
rg -nP 'MAX_CHANNELS_PER_FIXTURE' -C2 wled00/const.h

# Ensure no other code assumes DV bytes exist in legacy EEPROM space
rg -nP 'EEPROM\.read\((255[0-9]|256[0-9])\)' -C2

Length of output: 563

🏁 Script executed:

head -n 100 wled00/wled_eeprom.cpp

Length of output: 2696

🏁 Script executed:

#!/bin/bash
sed -n '340,430p' wled00/wled_eeprom.cpp

Length of output: 3156

Refactor DMXStartLED back-compat and bounds checking

  • Read the high byte at EEPROM 2551 only for EEPROM versions ≥ 17 (DMX support) and treat it as zero otherwise.
  • After computing DMXStartLED, clamp it to MAX_LEDS – 1.
  • Optional: zero-initialize any extra DMXFixtureMap slots and skip reading DMXChannelsValue for EEPROM versions before DMX was introduced (EEPVER < 17) to avoid stale data.
🤖 Prompt for AI Agents 
In wled00/wled_eeprom.cpp around lines 351-357, update the DMX EEPROM reads to
be backward-compatible and safe: only read the high byte at address 2551 when
the stored EEPROM version (EEPVER or equivalent eepromVersion variable) is >=
17, otherwise treat the high byte as zero; after combining low and high bytes
compute DMXStartLED and clamp it to the valid range (0 .. MAX_LEDS-1); for
DMXFixtureMap zero-initialize any slots beyond previously-used count to avoid
stale data; and if EEPROM version < 17 skip reading DMXChannelsValue entries
(leave them zero) to prevent loading pre-DMX garbage.

#endif

//Usermod memory
//2551 - 2559 reserved for Usermods, usable by default
//2560 - 2943 usable, NOT reserved (need to increase EEPSIZE accordingly, new WLED core features may override this section)
//2571 - 2579 reserved for Usermods, usable by default
//2580 - 2943 usable, NOT reserved (need to increase EEPSIZE accordingly, new WLED core features may override this section)
//2944 - 3071 reserved for Usermods (need to increase EEPSIZE to 3072 in const.h)
}

Expand Down
7 changes: 6 additions & 1 deletion wled00/wled_server.cpp
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Expand Up @@ -134,10 +134,15 @@ static String dmxProcessor(const String& var)
mapJS += F(";\nLC=");
mapJS += String(strip.getLengthTotal());
mapJS += F(";\nvar CH=[");
for (int i=0; i<15; i++) {
for (int i=0; i<MAX_CHANNELS_PER_FIXTURE; i++) {
mapJS += String(DMXFixtureMap[i]) + ',';
}
mapJS += F("0];");
mapJS += F(";\nvar DV=[");
for (int i=0; i<MAX_CHANNELS_PER_FIXTURE; i++) {
mapJS += String(DMXChannelsValue[i]) + ',';
}
mapJS += F("0];");
}
return mapJS;
}
Expand Down
26 changes: 11 additions & 15 deletions wled00/xml.cpp
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Expand Up @@ -634,21 +634,17 @@ void getSettingsJS(byte subPage, Print& settingsScript)
printSetFormValue(settingsScript,PSTR("CS"),DMXStart);
printSetFormValue(settingsScript,PSTR("SL"),DMXStartLED);

printSetFormIndex(settingsScript,PSTR("CH1"),DMXFixtureMap[0]);
printSetFormIndex(settingsScript,PSTR("CH2"),DMXFixtureMap[1]);
printSetFormIndex(settingsScript,PSTR("CH3"),DMXFixtureMap[2]);
printSetFormIndex(settingsScript,PSTR("CH4"),DMXFixtureMap[3]);
printSetFormIndex(settingsScript,PSTR("CH5"),DMXFixtureMap[4]);
printSetFormIndex(settingsScript,PSTR("CH6"),DMXFixtureMap[5]);
printSetFormIndex(settingsScript,PSTR("CH7"),DMXFixtureMap[6]);
printSetFormIndex(settingsScript,PSTR("CH8"),DMXFixtureMap[7]);
printSetFormIndex(settingsScript,PSTR("CH9"),DMXFixtureMap[8]);
printSetFormIndex(settingsScript,PSTR("CH10"),DMXFixtureMap[9]);
printSetFormIndex(settingsScript,PSTR("CH11"),DMXFixtureMap[10]);
printSetFormIndex(settingsScript,PSTR("CH12"),DMXFixtureMap[11]);
printSetFormIndex(settingsScript,PSTR("CH13"),DMXFixtureMap[12]);
printSetFormIndex(settingsScript,PSTR("CH14"),DMXFixtureMap[13]);
printSetFormIndex(settingsScript,PSTR("CH15"),DMXFixtureMap[14]);
for (int i = 0; i < MAX_CHANNELS_PER_FIXTURE; i++) {
char buf[5];
snprintf_P(buf, sizeof(buf), PSTR("CH%d"), i+1);
printSetFormIndex(settingsScript,buf,DMXFixtureMap[i]);
}

for (int i = 0; i < MAX_CHANNELS_PER_FIXTURE; i++) {
char buf[5];
snprintf_P(buf, sizeof(buf), PSTR("DV%d"), i+1);
printSetFormValue(settingsScript,buf,DMXChannelsValue[i]);
}
}
#endif

Expand Down