I have a circuit where I am using a SIM900 GSM/GPRS module. As per the datasheet it needs 3.4 V - 4.8 V and upto 2 A of current. I am using LM2576. The input to the regulator is 12 V & 4.2 A and output (which is going to SIM900) is 4.175 V. I have connected leds for NETLIGHT and STATUS LIGHT. I have connected a switch between PWRKEY and GND to start the SIM900. Following is the schematic of regulator:

1.png

SIM900:

2.png

The problem I am facing is as soon as I press the switch S1 to turn on the SIM900, its netlight led starts blinking and status light led is always off. There is no high voltage on status pin. I know that the net light blinks for network registration but this kind of blinking is not the expected behaviour of net light. It blinks twice a second and when I release the switch, it stops blinking. Status pin is always low. I checked the voltage. voltage seems to be stable on VBAT pins. Initially I am giving it 4.175v and when I press the switch it becomes 4.15-4.17v. I tried reflashing the firmware but during the process, it shows following error

error.png

In above pic it says that Target responding.. Does this means the SIM900A is in working condition because I was thinking that SIM900A is faulty.
What else could be the reason for this kind of behaviour. How can I debug it.
Please help. Thanks