bcm2835_pull_config_set
bcm2835_pull_config_set(pc, pin, arg);
bcm2835_pull_config_set(pc, pin, BCM2835_PUD_OFF);
bcm2835_pull_config_set(pc, pin, BCM2835_PUD_DOWN);
bcm2835_pull_config_set(pc, pin, BCM2835_PUD_UP);