For most boards, adc channels 1 and 5 are PA1 and PA5. Not the F3. oh no, that board is cray cray. PA0 and PF4 https://github.com/libopencm3/libopencm3/pull/471 https://github.com/libopencm3/libopencm3/pull/457 https://github.com/libopencm3/libopencm3/pull/534 https://github.com/libopencm3/libopencm3/issues/456 https://github.com/libopencm3/libopencm3/issues/455 https://github.com/libopencm3/libopencm3/issues/454