FAQ 2G Power On Modem

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Ques) LED D2 on the cape is not glowing after powering up the Beaglebone black plus cape setup?

Ans) 1) Ensure setup was powered up initially using a DC adapter (5V, 2.5A min) only.

2) Ensure the power jumper (#12 on leaflet) is present.


Ques) LED D3 is not glowing?

Ans) 1) Ensure the value of the GPIO pins 45 and 60. Both should be high.

2) Ensure that the modem is powered on.


Ques) How do I change the value of the 45 GPIO pin or any other GPIO?

Ans) 1) Make sure that first you have been able to export the gpio pin and then only you are trying to change the value, if not then you can do it by: 

cd /sys/class/gpio | echo 45 export


Ques) What are the serial port settings in minicom for accessing the port?

Ans) Serial device : /dev/ttyO1 ( corresponding dtbo file has to be loaded from /lib/firmware to /sys/devices/bone_capemgr.9/slots)

Bps/Par/Bits : 115200 8N1

Hardware and software flow control : none


Ques) What are some common useful AT commands to ensure 3G modem is working?

Ans) Some common AT commnds :

1) AT = Output “OK” if modem is on.

2) AT+CPIN? = Outputs the status whether sim card is detected or not.

3) AT+CREG? = To check if sim card is registered or not.

4) AT+COPS? = Operator selection.

5) AT+CSQ = Outputs Signal strength.

For more information and full set of information use : AT Commands Manual

Ques) What all should I ensure before establishing the connection?

Ans) 1) Cape is mounted properly on the beaglebone board.

2) You are logged in as root.

3) Initialization and Presence of UART1 port(/dev/ttyO1).

4) D4 should be high and the state of D4 is according to the status on the availability of the sim card.


Ques) What are the GPIOs for Resetting or turning ON/OFF the Modem and the GPS module?

Ans) For turning the Modem On or Off, GPIO45 is used. GPIO45 should be high by default.

For Soft Resetting, cycle GPIO45 through OFF and then ON .

For Hard Resetting the modem, GPIO60 is used. GPIO60 should be high by default

For Resetting the GPS module, GPIO50 is used. GPIO50 should be high by default.

There is no ON/OFF control for GPS Module.

Alternatively, push button switches can be used instead of GPIOs but all the GPIOs should be configured as output High as their default state.


Ques) What is the function of each LED? What do they denote and how do they function under different conditions?

Ans) D2 is power Led of Cape, which denotes the 5V power being provided to Cape and for the Modem.

D7 is 3.3V power LED from the Beaglebone Black. This denotes 3.3V power for GPS module and other ICs on Cape.

D5 is 1 PPS Fix led for the GPS module. It will blink at the rate of 1Hz, when GPS module has got its fix.

D4 is Netlight/Signal Led for the 2G/3G Modem. It has different behaviours depending on the state of Modem. For 3G modems, it is an optional feature. Ask for this feature while ordering.

D3 is Status LED for the GPRS Modem. It gives the indication whether the GPRS Modem is on or not. It glows continuously when the Modem is Turned ON and stays off when the Modem is turned OFF


Ques) What are the functions of the different Switches?

Ans) S1 is ON/OFF push button switch for the Modem.

S2 is Hard Reset push Button switch for the Modem.

S3 is Reset push button switch for the GPS module. S4 is 2 position DIP switch for specifying address for the EEPROM IC of cape on I2C2 bus of Beaglebone Black.

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