I'm making a project that involves interfacing with a SIM900A to send SMS messages.
I have purchased the following item:
http://www.ebay.co.uk/itm/SIM900A-5...225639?hash=item4d440da0e7:g:FnAAAOSwubRXNFiB
The seller is not technical, and is probably just a reseller or distributor - he couldn't answer my question.
To keep things simple, I've connected the SIM900A directly to the serial port of my PC (using on-board MAX232), but the actual project will be on an AVR. The SIM900A is provider locked to Asian countries, so I have flashed original SIM900 firmware (worldwide unlocked) to the board, which works fine. I can communicate with it no problem, all responses respond "OK", except the SIM card is never recognised. It's worth noting however that I had the same problem before I changed from the original SIM900A firmware, so this is unlikely the problem.
On power up I receive the following message in the console:
... which indicates that the SIM card is not detected (regardless of provider lock). I have the circuit powered by 5V 2A supply, more than adequate. I have been reading that the SIM card expects 3V3 to power up.
Pin 30 of the SIM900 (SIM_VDD) measures 0v. I have looked up the pinout of the SIM connections themselves and directly soldered 3V3 power to the SIM, but this doesn't seem to make a difference.
Am I being stupid? Should I be providing the 3V some other way? On the eBay listing it says:
Datasheets here:
http://www.amuroboclub.in/downloads/ebooks/GSM_MANUAL_SIM900_Hardware Design_V2.00.pdf
http://www.espruino.com/datasheets/SIM900_AT.pdf
I have purchased the following item:
http://www.ebay.co.uk/itm/SIM900A-5...225639?hash=item4d440da0e7:g:FnAAAOSwubRXNFiB
The seller is not technical, and is probably just a reseller or distributor - he couldn't answer my question.
To keep things simple, I've connected the SIM900A directly to the serial port of my PC (using on-board MAX232), but the actual project will be on an AVR. The SIM900A is provider locked to Asian countries, so I have flashed original SIM900 firmware (worldwide unlocked) to the board, which works fine. I can communicate with it no problem, all responses respond "OK", except the SIM card is never recognised. It's worth noting however that I had the same problem before I changed from the original SIM900A firmware, so this is unlikely the problem.
On power up I receive the following message in the console:
Code:
:+CPIN: NOT INSERTED
Pin 30 of the SIM900 (SIM_VDD) measures 0v. I have looked up the pinout of the SIM connections themselves and directly soldered 3V3 power to the SIM, but this doesn't seem to make a difference.
Am I being stupid? Should I be providing the 3V some other way? On the eBay listing it says:
But the board itself only seems to have VCC5. Please help!
- Two power supply interface: VCC5, 5V DC above 1A. Computer 5V power supply can be early computer USB. DC long data circuit over larger recommended 5V1A. VCC4, 3.5--4.5V power supply, ibid., suitable for lithium battery.
Datasheets here:
http://www.amuroboclub.in/downloads/ebooks/GSM_MANUAL_SIM900_Hardware Design_V2.00.pdf
http://www.espruino.com/datasheets/SIM900_AT.pdf