ESP32: DisplayModel 1 causes reboot with JMD0.96D-1 (SSD1306 I2C OLED, 0x3C) – works on older Tasmota

[rieders]

Summary of OLED Display Issue on ESP32-WROOM-32 (Tasmota 15.x)

Hardware Setup

• Controller board: ESP32-WROOM-32 (classic module, D0WD core)
• Display: JMD0.96D-1 OLED – 0.96", 128×64 pixels
  • Connection: I²C (SDA = GPIO21, SCL = GPIO22, address 0x3C)
  • SSD1306 / SH1106 compatible
• Power: 3.3V
• Test devices:
  • ESP32-WROOM-32 (tested multiple units)
  • Wemos D1 mini (ESP8266) – used for comparison

Firmware Versions Tested
Platform | Firmware | Result
ESP32-WROOM-32 | Tasmota 15.1.0.1 (tasmota32) | Display driver crash / reboot
ESP8266 (D1 mini) | Tasmota 9.2 (tasmota-display) | Display works perfectly

Wiring (I²C OLED)
OLED Pin | ESP32 Pin | Function
GND | GND | Ground
VCC | 3V3 | Power
SCL | GPIO22 | I²C Clock
SDA | GPIO21 | I²C Data

I2CScan → Device(s) found on bus1 at 0x3C

Test Results

Working (Tasmota 9.2 – ESP8266)
DisplayModel 2
DisplayDimmer 100
Display 1 Hallo Welt
Display 2 OLED active
Display → {"Model":2,"Width":128,"Height":64}

Failing (Tasmota 15.1.0.1 – ESP32-WROOM-32)
I2CScan → Device(s) found on bus1 at 0x3C
DisplayModel 1 → immediate reboot
{"Info3":{"RestartReason":"Software reset CPU"}}
Display → {"Model":0,"Width":4,"Height":6,"Rows":2}
DisplayText [z0c0]Hallo Welt → {"Command":"Error","Input":"DISPLAYTEXT [z0c0]Hallo Welt"}

Additional Behavior

• DisplayDimmer, DisplayRotate, and DisplayClear are accepted, but OLED stays blank.
• Changing models results in no crash for some IDs but wrong parameters ("Width":4,"Height":6).

Analysis

• Hardware verified OK.
• Issue appears only on ESP32 builds of Tasmota 15.x.
• DisplayModel 1 causes software reset.
• Likely regression or memory issue in SSD1306/SH1106 driver mapping for ESP32 builds.
• Older 9.2 version works fine.

Working Configuration (Stable Setup)
Firmware: Tasmota 9.2 (tasmota-display)
Board: Wemos D1 mini (ESP8266)
DisplayModel 2
DisplayDimmer 100
DisplayRotate 0
Display 1 Time:%time%
Display 2 Date:%date%

Conclusion
Firmware regression in Tasmota 15.x (tasmota32) affecting SSD1306/SH1106 display driver on ESP32-WROOM-32.
When setting DisplayModel 1, device immediately reboots and display remains inactive.
Same OLED works perfectly on older ESP8266 firmware.

Suggested Fix / Investigation

• Check SSD1306/SH1106 driver initialization in ESP32 builds (15.x).
• Verify that DisplayModel 1 correctly maps to OLED driver.
• Test with JMD0.96D-1 or SSD1306 module (0x3C I²C) on ESP32-WROOM-32.

Reproduce Summary
Board: ESP32-WROOM-32
Display: JMD0.96D-1 (SSD1306 128x64 I2C 0x3C)
Firmware: Tasmota 15.1.0.1 (tasmota32)
Steps:

1. I2CScan → 0x3C detected
2. DisplayModel 1 → immediate reboot
3. Display → Model:0, Width:4, Height:6
4. the pin setup is gone

Notes

• Tested on multiple ESP32-WROOM-32 modules
• Same wiring works perfectly on ESP8266
• Regression is repeatable and hardware-independent

[sfromis]

With current Tasmota versions, don't use the DisplayModel command to try to change anything, only to see what you have, which should always be model 17 if you have configured correctly for the Universal Display Driver. This means having the right display descriptor, and Option A 3 on an unused gpio.
https://tasmota.github.io/docs/Universal-Display-Driver/#universal-display-driver-udisplay