serial port signal path

Jan 28, 2026 Last reply: 5 months ago 1 Replies
B

Does anybody happen to know how data travels between gpio pins



8 and 10 and the system console? In other words, what hardware and maybe software facilitate the exchange? For example, the internal ethernet adapter is connected to the CPU via USB. Is something analogous for the system console?

I'm seeing what look like console failures on older-model Pi2s (v1.1) and wondering if some accessory subsystem, (usb comes to mind but I don't think that's it specifically) when running FreeBSD-current. The machine stops without complaint or warning, does not answer ping and has to be power cycled.



Thanks for reading,



bob prohaska



Vote
Twitter Facebook LinkedIn
C

I know with the BCM2835 (Pi 1 and Zero) both the UARTs (serial ports) are part of the SoC, as described in the peripherals documentation (often called the datasheet, though it's not really). They're "peripherals", but part of the chip so the signals connect directly - definitely no USB interface in-between. Other RPis _could_ be different but it's extremely unlikely because at least one UART peripheral is pretty essential, even just during product development.

Even though it's part of the same SoC as the CPU and other things, the UART is still something that can fail or be misconfigured even if there's nothing like USB in-between. Running a program/script that toggles the power light on/off (or another GPIO signal that you monitor) would indicate whether the CPU is still running when the serial console hangs.

Since it doesn't respond to a ping either, that suggests that it's probably crashed completely.

Vote
Twitter Facebook LinkedIn

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required