On Raspberry Pi boards, when the CPU is in halt state (powered, but CPU not running), GPIO3 is kept in high state due to an external pull-up resistor. Whenever GPIO3 is pulled low in this state ...

For the garden variety of TTL parts, and for all of them in my opinion, a pull-up resistor should always be used. Advertisement. 1 comment on “ Pull-up Resistors ” John Dunn February 14, 2014. If only ...