//measure rc time to charge to '1' on RC_READ pin
uint32_t rctmr_get(uint8_t ch_pin) {
    uint32_t tmp;
    IO_IN(RC_DDR, ch_pin);                  //discharge. ch_pin idles high/input
    IO_OUT(RC_DDR, RC_READ);                //discharges the capacitor (RC_READ idles low/output)
    while (IO_GET(RC_PORTIN, RC_READ)) continue;    //until the capacitor is fully discharged
    IO_OUT(RC_PORT, ch_pin);                //start to charge through the ch_pin
    IO_IN(RC_DDR, RC_READ);                 //start to charge up the capacitor
    tmp = ticks();                          //time stamp tmp
    while (IO_GET(RC_PORTIN, RC_READ)==0) continue; //wait for READ pin to go high
    tmp = ticks() - tmp;                    //measure the time elapsed
    IO_OUT(RC_DDR, RC_READ);                //discharge the capacitor
    IO_IN(RC_DDR, ch_pin);                  //start to discharge from the charge pin (idles high / input)
    return tmp;
}