[SOLVED] SIM900 SMS reception trouble

[Leopard77]

Hello, I've got the following trouble.

I've got a SIM900 on a board. Everything works great till I receive an SMS.

Everytime the SIM900 receives a SMS, the SMS is stored on the SIM card (I can read it on a normal phone) but the SIM900 module then turns off without any warning message sent...

I think that the network does not receive an answer from the SIM900. When I read the SIM on a normal phone the message appears as many times as I have performed a SIM900 power up...

When the SIM has been inserted in a normal phone, I can put it back in the SIM900 and everything works great till next attempt to receive a SMS.

Anybody has an idea of what is wrong ?

Thanks.

 

[horace1]

check your power supply - when transmitting the device can draw a lot of current which maygive a drop in supply voltage and cause the device to reset or switch off

 

[Leopard77]

Reading a lot about SIM900 I was aware of the power supply needs. Today my board is powered with a 5V 2A AC/DC adapter.
As I have no trouble in sending SMS, is it possible that the current draw could be higher in SMS reception than in SMS sending ?

- - - Updated - - -

The voltage on my board is shifted to 4.1V by a MIC2903 according to SIM900 Hardware Design. I've got only a digital multimeter, but according to its reading I have no drop in voltage during all the process. 4.1V sharp...

 

[horace1]

there are some guidelines to the power supply in section 4.1 of the datasheet
**broken link removed**

a power supply of 2amps should be sufficent when transmitting

 

[Leopard77]

I have only a digital multimeter but I've check either voltage and current flow during process and I cannot see any trouble. 4.1V sharp and 280mA till the SIM900 shuts down...

Does anybody has another idea ? Any chance to get debugging message from SIM900 before shut off ?

I've just check with a 5V / 45A power supply and it's still going wrong :roll:

 

[Leopard77]

Hello everybody. I've bought the very same board again and now everything is going well. I must admit that I couldn't imagine that a chip could have only a small part of functionnality going wrong...