SIM Card issues of product prototype using EC21-AU

I posted a question of SIM card detection problem in EC21-AU module. It always reports error “SIM Card Not inserted”. Unfortunately, nobody replied any solution of the question. Maybe there are similar questions in the forum. The answers cannot get help for my case anyway.

By checking the PCB layout, the traces of USIM_DATA and USIM_CLK are very close in the layout. Will it be a cause of SIM detection failed ?

Will it be an firmware problem in the EC21-AU ?

I would be grateful if any expert can help me.

Many thanks.

1)Please try to replace another SIM card, if the output is the same alarm, it may be caused by your PCB
2)You can also solder the SIM pin of the EC21 out and connect to the SIM card holder and try to read if the card is working

Thanks for your reply.

I have replaced by another SIM card. It is the same. I did solder the SIM pins of the EC21 out and connected directly to a SIM card. It is still not able to detect the SIM card. Will the PCB layout problem affect the SIM detection although I soldered the SIM directly to the SIM pins of EC21 ?

I did some more testing. I cut the traces from SIM card socket and directly solder the SIM card to EC21AU. It is still not able to detect the SIM card. I did the same work in a Sixfab shield it works. It may be the EC21AU problem. Can I get the latest firmware of EC21AU ?

Please provide your current firmware version

The firmware version is : EC21AUFAR02A04M4G

We have 12 EC21AU samples. All of them have SIM card detection problem.

it is the latest firmware in baseline

Thanks. Then what causes the SIM detection issue. Is the SIM interface of the module damaged ?

It is impossible to determine the specific reason through your description, and you need to cross-verify by replacing the SIM card holder and other methods

I think you should try to measure the traces for the SIM card and verify that they have “appropriate” values. SIM_VDD, clock, correct ground…

@CarlosR_5COMM , thanks for your advice. I have done the measurement already. SIM_VDD is 0V, both clock and data are 0V without any signal. Ground is connected correctly to the main ground plane of the circuit.

The one time we had a similar issue the ESD array was placed incorrectly resulting in shorting some SIM traces to ground.