I am working with a Pixhawk 4 and a Spektrum AR620 receiver. The receiver has a 3x7 grid of pins labelled (-, +, S), and (Batt, 1-6). The reciever says it is a DSM2/DSMX receiver, and I want to connect it to the DSM port of my flight controller. However I am unsure what connections are supposed to be made. Where do I attach the DSM connector wire to the receiver? I tried attaching the dsm header to channel one of the reciever, but then QGroundControl (my mission planner) couldn't read anything from it. The receiver is bound to the transmitter (spektrum DX6i), even while connected to the pixhawk. It is definately reciever signals too (as measured by a voltmeter applied to the signal wire and checking the voltage changed with respect to transmitter movements.) However this was done before hand, and then I plugged it into the pixhawk. The spektrum bind button gives an error "vehicle did not respond to command: MAV_CMD_START_RX_PAIR", no matter what mode I attempt to start it in (I realize this isn't necessary because it is already bound, but I am trying everything). Most of the pixhawk settings are still default, except I set SYS_USE_IO to 0 so that I could use my main motors in the FMU out. The ACT light of both IO and FMU are constantly flashing blue. I am using a basic quad frame. I have tried many steps including holding switch, reflashing firmware, etc. I still recieve the same error, "0 channels detected. To operate pixhawk you need at least 5 channels"
Edit-- Pictures of Reciever and FC connections