Wrong colors on ILI9488 with 8-bit parallel (I80) interface since uDisplay refactor

[augea]

Wrong colors on ILI9488 with 8-bit parallel (I80) interface since uDisplay refactor

After upgrading from Tasmota 15.0.1.1 to 15.3.0.3, the ILI9488 display connected via 8-bit parallel (I80) interface on an ESP32-S3 shows wrong colors: blue appears as green, and the overall color palette is severely reduced (appears to be ~16 colors instead of 65K). The same display.ini worked perfectly on Tasmota 15.0.1.1.

SPI-connected ILI9488 displays are not affected — only the parallel (I80) interface path is broken.

Symptoms:

Symptom	Detail
Blue → Green	Pure blue backgrounds appear green
Reduced colors	Display looks like ~16 colors instead of 65K (RGB565)
LVGL Mirror	Shows correct colors (confirms LVGL renders correctly)
SPI display	Same ILI9488 via SPI on ESP32-D0WD works correctly
Tasmota 15.0.1.1	Worked perfectly with identical display.ini
Tasmota 15.3.0.3	Broken (both master and development branch)

Root Cause:

The uDisplay driver was refactored in PR #24007 (Oct 2025), splitting the monolithic uDisplay.cpp into panel-specific files. During this refactoring, the byte order logic for 8-bit parallel (I80) pixel pushing was inverted.

The bug is in I80Panel::pushColors() in lib/lib_display/UDisplay/src/uDisplay_I80_panel.cpp, line ~264:

bool I80Panel::pushColors(uint16_t *data, uint32_t len, bool swapped) {
    pb_pushPixels(data, len, !swapped, false);  // <-- BUG: the '!' inverts byte order
    return true;
}

The call chain:

1. LVGL flush calls uDisplay::pushColors(data, len, not_swapped=true) — comment in uDisplay_graphics.cpp: "not_swapped is always true in call from LVGL driver!!!!"
2. uDisplay::pushColors calls universal_panel->pushColors(data, len, not_swapped=true)
3. I80Panel::pushColors(data, len, swapped=true) calls pb_pushPixels(data, len, !true=false, false)
4. pb_pushPixels with swap_bytes=false sends: low byte first, then high byte — but ILI9488 expects high byte first

In the old monolithic uDisplay.cpp (15.0.1.1), the PAR8 path always used pb_pushPixels(data, len, true, false) with swap_bytes=true, producing the correct byte order.

Byte order on the 8-bit bus for RGB565 — Pure Blue (0x001F):

Code path	1st byte on bus	2nd byte on bus	Display sees
Old code (correct)	0x00 (RRRRRGGG)	0x1F (GGGBBBBB)	R=0, G=0, B=31 → Blue
New code (broken)	0x1F (GGGBBBBB)	0x00 (RRRRRGGG)	R=0, G=56, B=0 → Green

Note: The comment on line ~264 says "swap_bytes=true to match old driver", which confirms the intent was to have swap_bytes=true — but the ! negation produces the opposite result.

Proposed Fix:

In lib/lib_display/UDisplay/src/uDisplay_I80_panel.cpp, line ~264, remove the ! negation:

// Before (broken):
pb_pushPixels(data, len, !swapped, false);

// After (fixed):
pb_pushPixels(data, len, swapped, false);

Workaround (display.ini):

Until the fix is merged, setting swap_color bit in the :B parameter compensates for the inverted logic:

:B,20,2    (was: :B,20,0)

This sets bit 1 (swap_color=1) in LVGL_PARAMS_t.data, which adds an additional not_swapped = !not_swapped inversion in uDisplay::pushColors() before calling the I80 panel, canceling out the erroneous ! in the I80 code. This workaround must be reverted back to :B,20,0 once the source code fix is applied.

Affected Versions:

• Tasmota master (v15.3.0): Bug present
• Tasmota development: Bug present (identical code)
• Tasmota 15.0.1.1: Not affected (old monolithic uDisplay.cpp)

REQUESTED INFORMATION

• Read the Contributing Guide and Policy and the Code of Conduct
• Searched the problem in issues
• Searched the problem in discussions
• Searched the problem in the docs
• Searched the problem in the chat
• Problem is not scripter related, in this case open a discussion and tag gemu2015
• Device used (e.g., Sonoff Basic): Custom ESP32-S3 board with ILI9488 (8-bit parallel) + FT6236 touch
• Tasmota binary firmware version number used: 15.3.0.3
  • Pre-compiled
  • Self-compiled
• Flashing tools used: PlatformIO (esptool via USB)
• Provide the output of command: Backlog Template; Module; GPIO 255:

{"NAME":"ESP32S3","ARCH":"ESP32S3","GPIO":[1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1,1],"FLAG":0,"BASE":1}
{"Module":{"1":"ESP32S3"}}
GPIO8: I2C SDA1 (640)
GPIO9: I2C SCL1 (608)
GPIO10: Switch1 (160)
GPIO11: Relay1 (224)
GPIO45: Option A3 (6210)
(all other GPIOs: None — display pins configured via display.ini, not GPIO template)

• If using rules, provide the output of this command: Backlog Rule1; Rule2; Rule3:

No rules — Berry/LVGL application, rules disabled in build (#undef USE_RULES)

• Provide the output of this command: Status 0:

{"Status":{"Module":1,"DeviceName":"Tasmota-DispP","FriendlyName":["Tasmota-DispP",""],"Topic":"tasmota_217DF8","ButtonTopic":"0","Power":"00","PowerLock":"00","PowerOnState":3,"LedState":1,"LedMask":"FFFF","SaveData":1,"SaveState":1,"SwitchTopic":"0","SwitchMode":[1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],"ButtonRetain":0,"SwitchRetain":0,"SensorRetain":0,"PowerRetain":0,"InfoRetain":0,"StateRetain":0,"StatusRetain":0},"StatusPRM":{"Baudrate":115200,"SerialConfig":"8N1","GroupTopic":"tasmotas","OtaUrl":"http://ota.tasmota.com/tasmota32/release/tasmota32s3.bin","RestartReason":"Software reset CPU","Uptime":"0T00:05:50","StartupUTC":"2026-03-23T10:22:51","Sleep":50,"CfgHolder":4617,"BootCount":797,"BCResetTime":"2025-06-16T19:23:11","SaveCount":4351},"StatusFWR":{"Version":"15.3.0.3(tasmota)","BuildDateTime":"2026.03.23 09:59:06","Core":"3.3.7","SDK":"5.3.4.260127","CpuFrequency":240,"Hardware":"ESP32-S3 v0.2","CR":"423/699"},"StatusLOG":{"SerialLog":3,"WebLog":2,"MqttLog":0,"FileLog":0,"SysLog":0,"LogHost":"","LogPort":514,"SSId":["RAPTOR1",""],"TelePeriod":300,"Resolution":"558180C0","SetOption":["0000C009","0A05C80001000600003C5A0A1928FA000000","40008080","04006000","00004001","00000000"]},"StatusMEM":{"ProgramSize":2208,"Free":4959,"Heap":108,"StackLowMark":17,"PsrMax":6016,"PsrFree":5706,"ProgramFlashSize":16384,"FlashSize":16384,"FlashChipId":"184046","FlashFrequency":80,"FlashMode":"QIO","Features":["0407","87BAC7CF","001482A1","000214CF","014017F1","C0000981","000040A0","00200000","5400002C","00020080","00000004"],"Drivers":"1,2,!3,!4,!5,7,!8,9,12,13,!16,!20,!21,!24,26,27,29,!35,38,50,52,54,55,56,62,!67,!68,!121","Sensors":"1,2,3,5,6,9,10,14,29,42,127","I2CDriver":"3,5,7,10,11,15,22,26,29,47,77"},"StatusNET":{"Hostname":"tasmota-217DF8-7672","IPAddress":"192.168.168.105","Gateway":"192.168.168.1","Subnetmask":"255.255.255.0","DNSServer1":"192.168.168.131","Mac":"30:ED:A0:21:7D:F8","Webserver":2,"HTTP_API":1,"WifiConfig":4,"WifiPower":19.0},"StatusMQT":{"MqttHost":"raspberrypi5","MqttPort":1883,"MqttClientMask":"DVES_%06X","MqttClient":"DVES_217DF8","MqttUser":"master","MqttCount":1,"MqttTLS":0,"MAX_PACKET_SIZE":1200,"KEEPALIVE":30,"SOCKET_TIMEOUT":4},"StatusTIM":{"UTC":"2026-03-23T10:28:42Z","Local":"2026-03-23T11:28:42","StartDST":"2026-03-29T02:00:00","EndDST":"2026-10-25T03:00:00","Timezone":"+01:00","Sunrise":"06:46","Sunset":"19:06"},"StatusSNS":{"Time":"2026-03-23T11:28:42","Switch1":"OFF","BME280":{"Temperature":23.7,"Humidity":34.5,"DewPoint":7.1,"Pressure":989.1},"BH1750":{"Illuminance":56},"SHT3X":{"Temperature":23.2,"Humidity":40.2,"DewPoint":8.9},"SCD30":{"CarbonDioxide":975,"eCO2":998,"Temperature":25.8,"Humidity":35.1,"DewPoint":9.2},"Shutter1":{"Position":0,"Direction":0,"Target":0,"Tilt":0},"PressureUnit":"hPa","TempUnit":"C"},"StatusSTS":{"Time":"2026-03-23T11:28:42","Uptime":"0T00:05:51","UptimeSec":351,"Heap":108,"SleepMode":"Dynamic","Sleep":10,"LoadAvg":99,"MqttCount":1,"Berry":{"HeapUsed":230,"Objects":3056},"POWER1":"OFF","POWER2":"OFF","Wifi":{"AP":1,"SSId":"RAPTOR1","BSSId":"34:81:C4:F2:1C:A1","Channel":1,"Mode":"HT20","RSSI":82,"Signal":-59,"LinkCount":1,"Downtime":"0T00:00:03"},"Hostname":"tasmota-217DF8-7672","IPAddress":"192.168.168.105"}}

• Set weblog to 4 and then, when you experience your issue, provide the output of the Console log:

Not applicable — this is a pixel byte-order issue in the display driver, not a runtime error.
The display initializes and renders without errors. Colors are simply wrong due to
swapped byte order on the 8-bit parallel bus.

TO REPRODUCE

1. Use an ILI9488 display with 8-bit parallel (I80) interface on ESP32-S3
2. Configure display.ini with :H,ILI9488,480,320,16,PAR,8,... and 3A,1,55 (RGB565)
3. Enable LVGL (Berry or HASPmota)
4. Observe that blue backgrounds appear green and the color palette is severely reduced

The issue does not occur with:

• SPI interface (3A,1,66 + :P,18) — SPI path has its own color conversion, unaffected
• Tasmota 15.0.1.1 or earlier (before the uDisplay refactor)

EXPECTED BEHAVIOUR

Colors should be displayed correctly on 8-bit parallel (I80) ILI9488 displays, as they were in Tasmota 15.0.1.1. Blue should appear blue, not green. The full 65K color palette (RGB565) should be visible.

The one-character fix (removing ! from line ~264 in uDisplay_I80_panel.cpp) restores correct behavior:

pb_pushPixels(data, len, swapped, false);  // remove the '!' before 'swapped'

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SCREENSHOTS

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ADDITIONAL CONTEXT

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