I have used a 5V 3A powersupply from Conrad
https://www.conrad.nl/nl/hn-power-hnp18-050-c-stekkernetvoeding-vaste-spanning-5-vdc-3000-ma-512693.html
although i think 2A is good enough. I have connected it to the PI-pins 4(+5V) and 6(gnd).
Connections RPI <=> IC880
+5V................2..........21
NSS..............26.........17 (i have rpi-24 but changed the source of poly-forwarder)
MOSI...........19..........16
MISO............21.........15
SCLK............23.........14
reset..............39.........13 =gnd - dont know what else to do with it
GND..............25........12
please doublecheck the connections for yourself.....
I will next connect an Adafruit ultimate GPS to the PI's rxd/txd and the IC880's PPS.
See what happens.....
succes,
Art