Recently, I decided to build my own cell phone out of an ODROID-GO Advance using a SIM800L module which included a speaker and mic. Thanks to the ample space inside the case, this hardware installation was pretty easy. For this build, I used a Debian Buster image with the SIM880L connected to the ODROID-GO Advance’s UART2.
Initially, I tried with minicom to communicate with /dev/ttyFIQ0 but I did not get an answer. I also tried the 10pin connector (UART1) but was unlucky there, as well. After some help from the Hardkernel forum, I learned that changes needed to be made in the device’s dtb file. The needed changes included disabling the ‘fiq-debugger’ which used UART2, and enabling that UART port as a common serial port. Additionally, the fiq-debugger device entry was removed from the boot.ini file. After those changes had been made and a reboot performed, AT-Commands could be sent with a response from the SIM module.
After some more work, a basic interface was created to hold contact information and manage calls.
For more information, the original forum thread is available at https://forum.odroid.com/viewtopic.php?f=193&t=38248.