I am creating a gate system using a Raspberry Pi Zero and a SIM800H (Adafruit Fona). I have been working on this project for about 2 years and feel quite comfortable with the software stack. Everything is done in Nodejs. Here is what happens when I call the SIM800H:
- I call the SIM800H.
- SIM800H responds with URC’s RING and +CLIP. As expected.
- I send ATH to the SIM800H to hangup the call.
- SIM800H responds with BUSY after about 200ms. <= what is this?
- SIM800H responds with OK after about 9ms. This is normal. As expected.
- The call is ended. As expected.
Now, what is the BUSY response from the SIM800H? I cannot find anything related to BUSY in the SIM800H documentation and I would like to know what is the cause for it.
Thank you in advance for flexing your brain for me