Pin 1 is the short pin on the left (if the card is to inserted forwards)
Pin 38 is the long pin on the right.
/CD is tied to ground in the HuCard, so the console knows if a card is inserted.
A cartridge can send audio on AUDIO_IN, it will be output equally on both left and right channels.
/HSM controls the clock: High=7.15909 Mhz, Low=1.7897725 Mhz.