ESP32-P4-PC: USB-JTAG instability and LT8912B I2C issue

Started by Rochus, October 17, 2026, 12:22:39 AM

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Rochus

While tying to migrate the Oberon System 3 to the P4-PC board I have hit the following road blocks (not sure whether this is the right place for this or it was already reported elsewhere):

Rev.C, behaviour reproduced on two separate boards

Not using any of your software or drivers

# 1. USB Serial/JTAG interface drops and re-enumerates continuously

Only started after several flashes and tests

/dev/ttyACM* node then appears and disappears every few seconds for some time with stable phases (~10 minutes) in between

# 2. LT8912B I2C interface strange behaviour when HDMI is connected

The LT8912B is on GPIO7/SDA + GPIO8/SCL

Once a monitor is attached, the LT8912B cannot be (re)configured

If the monitor is attached/detached after a working init, the LT
often loses its HDMI transmitter state and the display stays blue until the LT is re-initialized



LubOlimex

What is the hardware revision of the board that you use?
Technical support and documentation manager at Olimex