I have now got back to this topic. I installed wiringpi-v2.44-friendlyelec-rk3399.deb, "gpio readall" looks good. When I try to use the library to build an application I find it's not built with libcrypt. root@NanoPi-M4v2:/usr/src/pihpsdr# make gcc -o pihpsdr audio.o band.o discovered.o di...