There is a project in which Raspberry Pi 4 is connected to USB: K-line adapter (to get diagnostic information from the engine, on the chip ftdi), microcontroller stm32 in CDC mode (defined as a serial port) and 4G modem. RPI is powered from a car battery through a 12-5v 3A converter such as this The battery itself is charged from a car alternator. What is the problem: When the engine speed rises to 2500 and more: the diagnostic adapter starts to fall off. In dmesg I see: ftdi_sio ttyUSB0: usb_serial_generic_read_bulk_callback - urb stopped: -32 At revolutions about 4000, STM32 also falls off. The device itself is in place /dev/ttyACM0, there are no messages in dmesg, but data from it just stops coming. It is cured only by rebooting RPI. 4G modem is always working normally. It is with USB-Serial devices that the problems start. I tried to connect a completely different diagnostic adapter (ELM 327 with CH340 interface chip). The situation is exactly the same. Moreover, if the adapter is pulled out of USB at all, the STM32 stops falling off. Magic. I can't understand how it is all connected with each other. If there is not enough power on USB, then why 4G modem does not respond? And why should the power supply suddenly be insufficient, because the generator works more actively when revolutions increase on the contrary. The adapter is 3A, USB peripherals do not consume anything special. I changed the RPI board to another one - no difference.
Statistics: Posted by Lorman — Sun Jul 21, 2024 3:42 pm