I am trying to use my RaspberryPi Zero to communicate with an A6 GPRS module (http://www.inkocean.in/gprs-a6-module-sms-board-gsm-gprs-wireless-data-transmission-over-sim900a)
Drawing of physical connections:
- connect module's U_TDX pin to PiZero's TXD0 (GPIO14)
- connect module's U_RDX pin to PiZero's RXD0 (GPIO15)
- connect module's GND pin to PiZero's Ground
- power up pi using micro-usb
- power up module using it's own micro-usb port
- disabled serial port getty/logging using raspi-config
- added linux user to group dialout
ls -l /dev/ttyAMA0output:
crw-rw---- 1 root dialout 204, 64 Oct 19 10:17 /dev/ttyAMA0
Now I should be able to communicate with the module and monitor the serial port using a serial monitor, i have tried using screen for this:
screen /dev/ttyAMA0 115200
But I get a blank screen without errors.
According to this blog (https://learn.adafruit.com/fona-tethering-to-raspberry-pi-or-beaglebone-black/setup) which uses a similar module, i should be able to type "AT" + enter (without seeing the feedback of chars being typed) and I should receive "OK", which I do not.
- the module is borked (doesn't seem so; I get a solid red led and a blue led blinks a few times after boot, I assume it's making connection to the sim's network)
- wiring is incorrect, perhaps use different pins on the module?
- I have not yet correctly configured the serial monitor screen or am using the wrong baud rate?
What I have tried:
- connecting the zero's serial ports to the module's R232_RXD and R232_TXD ports
- using minicom as a serial monitor
- using PySerial to send/read data to/from the module
What I havn't tried:
- connecting the zero's serial ports to the module's H_RXD and H_TXD ports as I assume these are not the ports I need
Any help solving or even just debugging this issue would really be appreciated, as I am really stuck. Thanks.