use sudo su before checking the directory

found the answer
the modem is switched off by default,
use gpio mode 16 out
gpio write 16 1
to turn it on
and the serial will work fine

found the answer
to turn on the modem use sudo/root
gpio mode 16 out
gpio write 16 1

to turn on the gsm, u need to install wiringNP then use the following: sudo gpio mode 16 out sudo gpio write 16 1 for the sim800c-test.py file, u have to use the official image, and the instruction is in official wiki http://wiki.friendlyarm.com/wiki/index.php/NanoPi_Duo2_IoT-Box path is /root/Pytho...

you can try installing wiringNP and then use the Process class to run the gpio command eg: Process proc = new Process(); proc.StartInfo = new ProcessStartInfo("gpio", "mode 0 out"); proc.StartInfo.RedirectStandardOutput = true; proc.StartInfo.UseShellExecute = false; proc.Start()...

GSM can be connect at /dev/ttyS3
u can refer it in the sim800c-test.py file
PIN 11 for turning the power on
(if using wiringNP gpio command, try gpio mode 16 out)
after that you will see the blinking light for the GSM and u can use minicom to connect

it seems that the GSM is always off by default from the default sim800c-test.py we can find that the GSM_PWR is pin 11 and LED is pin 9 what command do i use from WiringNP to turn it on ? i tried gpio MODE 11 IN gpio MODE 9 OUT but nothing change when i use gpio readall to check what GPIO command sh...

following the instructions from http://wiki.friendlyarm.com/wiki/index.php/NanoPi_Duo2_IoT-Box#Work_with_GSM.2FGPRS_Module gives an error importing the serial. (apparently, pip install --upgrade pip is not a good idea, this will creates a import main issue which many are facing. so i omitted that st...