Hello,
Recently we made a prototype PCB which includes a BC66 module, a main MCU and a USIM card holder. Communication between the main MCU and the BC66 is going fine, however all SIM related commands are giving errors. These include: “AT+ QCIDD”, “AT+CPIN?”, “AT+CIMI”. See output below. The SIM card itself seems to work fine in other devices though.
That leads me to think there is a problem with the connection between the BC66 and the USIM card holder. See image below for schematics. I’ve also attached a reference design diagram from the BC66 hardware design guide. As far as I can tell our connections are correct, except for the missing TVS. Could that be a cause for problems?
We also forgot to add the POWER_KEY connector / button. So now I’m briefly holding a wire between GND and the PWR_KEY to power on the BC66.
hi,brixton:
The SIM card can be detected by your circuit design,although there are some differences from the reference design we provided.
I suggest you check the following aspects:
1、Do all devices have this problem, or does your current initial device have this problem?
2、You can solder the pin of the SIM card holder directly to the corresponding pin of the module to check whether the card holder is abnormal.
3、Check for short circuit or cross welding problems.
Thank you for the suggestions. I have tried with another PCB of the same batch, and it gives the exact same problems as the initial one.
I have also checked for welding and short circuit problems. Nothing seems to be out of the ordinary.
One thing I noticed is that when I connect to the debug UART port on the BC66 (using Putty), I receive no characters. I’m not able to use UE monitor because I don’t have a “message definitions file” for this module, but I would expect to at least see some characters coming through even without using UEMonitor. I find that strange, do you think that might be related to the problem?
hi,brixton:
1、I recommend that you weld the pin of the SIM card holder’s pin directly to the pin of the module. This is also allowed and can be used to troubleshoot your circuit design problems.
I had a similar SIM issue on a custom PCBA. The problem turned out to be that the orientation of how the SIM card needed to be inserted into the holder was different than I expected. The holder I was using required the SIM’s chamfered corner to be outward.
@herbert.pan-Q , I haven’t tried that yet because I don’t have such an external SIM connector. But I’ll see if I can get one.
I noticed that I was doing this wrong too, thanks for the suggestion! I’ve changed it around now, but it hasn’t made much difference unfortunately.
CFUN = 1. See logs.
what is CFUN value?
AT+CFUN?
+CFUN: 1
OK
USIM card identification - AT+QCCID
AT+QCCID
+CME ERROR: 772
USIM card identification - AT+QCCID
AT+QCCID
+CME ERROR: 772
Is a PIN needed for the SIM card? AT+CPIN?
AT+CPIN?
+CME ERROR: 772
Is a PIN needed for the SIM card? AT+CPIN?
AT+CPIN?
+CME ERROR: 772
Error 772 means that the USIM is powered down according to the manual. When I measure the voltage of SIM_VDD I measure 0 V. Strange behaviour. In this post it is explained that the voltage drops to 0 V after an initial startup sequence.
Hi,
I think need check sim holder,(sim cart) <-> module connection lines.
Replace 22 Ohm resistors to 0 Ohm, then unsolder all capacitors on SIM holder line.
Connect a Sim holder to module directly.
is SIM cart OK? Does it work in other solution?
Change module
Update: I removed all the capacitors from the SIM connection, and have also replaced the resistors to 0 Ohm as per @KvX suggestion. I also added a piece of paper above the SIM so that the Nano SIM card pushes harder against the pogo-pin-like contacts. Another thing I did is cut off a little bit from the corner (opposite the chamfer) of the nano SIM so that it goes into the SIM holder well and activates the clicking mechanism.
I also increased the power supply so that it is able to deliver 2 A worth of current if the module requires it.
yet, I still get the same response, +CME ERROR: 10.
Could it be that the SIM holder is not suited to NB IoT SIM cards? This is the one I’m using.
I bypassed the voltage regulator on the PCB, and connected it straight to a power supply capable of delivering 1 A. The PCB voltage reg only delivers 300 mA
I removed (with some plyers) R10, C16, C17, C15, C18, C23. See the schematics at the top of this post.
Good afternoon. problems with the SIM card. The tablet does not see the SIM card. model EG25GGCR07A02M1G. The SIM card is correctly positioned in the Card Receiver.