model: GPRS shield
Ardunio code: serial relay example,
back to microcontrollers page.
History / worklog
2021-08-12: I re-created this page on my self-hosted web server.
2015-02-25: a quick test with an Arduino Nano v3.0 too. I connect the Nano to a breadboard, connect GND and + 5V from the breadboard to the GPRS shield, and pins D7 and D8 from the breadboard to the GPRS shield. Again, I upload the "Serial Relay" example, and start the Serial Monitor, 19200 baud, carriage return. Test output:
AT OK ati SIM900 R11.0 OK
Does it have the problem with upper case for first command?
NORMAL POWER DOWN ÿÿÿÿÿÿÿÿAT OK ati SIM900 R11.0 OK
yes, it does - first command (the "AT" part at least) after poweron must be in upper case.
at+cpowd=1 NORMAL POWER DOWN
end of test.
2015-02-25: interesting, it seems that after power on (with the power key), the first command has to be "AT" (in upper case). If I send "at" I don't get a response, no matter how many times I send the command. The first time I send an upper case command (ATI for example) I get a response and "OK". After that I can send lower case commands too. Weird. It also seems that it is enough for the two first characters to be in upper case ("AT"), the rest of the command can be in lower case. Here is example output:
NORMAL POWER DOWN ÿÿÿÿÿÿÿÿATi SIM900 R11.0 OK
that's a bug I think.
2015-02-25: Next, I uploaded the "Serial Relay" example from the GPRS shield wiki page, started the Serial Monitor in Arduino IDE, selected 19200 and
"carriage return". typing AT
cool. Identify product:
ati SIM900 R11.0 OK
more? Query baud rates:
at+ipr=? +IPR: (),(0,1200,2400,4800,9600,19200,38400,57600,115200) OK
good. Various information:
(requires SIM card to be present)
at+gmi SIMCOM_Ltd OK at+gmm SIMCOM_SIM900 OK at+gmr Revision:1137B03SIM900M64_ST_ENHANCE OK at+goi SIM900 OK request IMEI: at+gsn 013949007158952 OK at+icf? +ICF: 3,3 OK
this means 8N1.
at+ifc? +IFC: 0,0 OK
no flow control.
at+ipr? +IPR: 0 OK
auto baud rate.
at+cbc +CBC: 0,95,4134 OK Battery charge: not charging (0), 95%, 4.134 volt. at+cpowd=1 NORMAL POWER DOWN
and after that I can't send commands any more.
2015-02-25: I disconnect the UNO from the usb cable, and connect UNO and GPRS shield. When I connect the UNO to usb again, the "green" (power) LED on the GPRS shield turns on. Man, it is bright. When I press the power button on the GPRS shield, the red LED (status) turns on, and the Net light blinks green (quickly). Note: I don't have a SIM card in the GPRS shield for this test.
2015-02-25: GPRS shield - I verified that it was set for SWserial (pin D7 and D8), and set power select to "from Arduino".
2015-02-25: I started by connecting the UNO to my Linux laptop and tested it with a modified version of the Blink example program - ok.
2015-02-25: test environment: Arduino UNO R3 (white board), Arduino 1.0.5 IDE.
2015-02-25: I borrowed this shield to test it.