From https://github.com/OpenIPC Wiki:
# devmem 0x20270110 32 0x60FA0000 ; devmem 0x20270114 8 | awk '{print "CPU temperature: " ((($1)*180)/256)-40}'
CPU temperature: 38.75
Source PDF:
Hi3518E V20X/Hi3516C V200 Economical HD IP Camera SoC
3.11.2 Operating Mode
Internal Temperature Detection