user-1: I bought this SIM800C development board (vendor unknow):


I conected it to an Arduino and put a brand new SIM card in it. This is the model of SIM I'm using:

Problem is, development board doesn't detect SIM card:
at+cfun=1,1    
OK
at+cpin?    
+CME ERROR: SIM not inserted
at+csmins?    
+CSMINS: 0,0

This is the scenario: 

6 pin SIM in a 6 pin SIM card holder.
SIM works fine in a cel phone. Send/receive voice call/sms.
Older, working SIM from various providers doesn't get detected either.
Every other non-SIM related aspect works.
No reboots, no flickering.
Board takes care of regulating voltages and signal levels.

I put an oscilloscope probe on the SIM_VDD pin (against board ground) and got this on every power-on:

Two 1.8v and two 3v pulses. That's all.
Please, note that I have no access to all SIM connexions (multi layer PCB).
How do I solve this problem?

user-1: The print on the PCB and product description at sellers site states it is GSM/GPRS board. The  module on the board comes from SIMCom. This particular SIM800 module seems to have following capabilities as per SIMCom:

Compliant to GSM phase 2/2+
GPRS multi-slot class 12/10
Quad-band 850/900/1800/1900MHz

I think at the best you can only use a 2G SIM card on this board. Any 3G/4G SIM will not work.
Thanks for those images in the problem description, it gave me relevant keywords to search.

-1: <p>I bought this <a href="https://www.aliexpress.com/item/SIM800-Development-Board-Module-Support-GSM-GPRS-3-3-5V-TTL-Level-Control-DC-6-24V/32798811432.html?spm=2114.01010208.3.9.lbFC5h&amp;ws_ab_test=searchweb0_0,searchweb201602_2_10152_10065_10151_10208_10068_10191_10136_10137_10060_10155_10062_437_10154_10056_10055_10054_10059_303_100031_10099_10103_10102_10096_10052_10053_10142_10107_10050_10051_10173_10084_10083_10080_10082_10081_10110_519_10111_10112_10113_10114_10182_10078_10079_10073_10123_10189_142,searchweb201603_16,ppcSwitch_5&amp;btsid=0bed8485-be65-423d-8aab-4b16ac2eedc9&amp;algo_expid=d79b8180-51bc-47bd-8e89-2267b6e579a3-1&amp;algo_pvid=d79b8180-51bc-47bd-8e89-2267b6e579a3" rel="nofollow noreferrer">SIM800C development board</a> (vendor unknow):</p>

<p><a href="https://i.stack.imgur.com/JmENO.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/JmENO.jpg" alt="Development board - front"></a>
<a href="https://i.stack.imgur.com/yA9gp.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/yA9gp.jpg" alt="Development board - back"></a></p>

<p>I conected it to an Arduino and put a brand new SIM card in it. This is the model of SIM I'm using:</p>

<p><a href="https://i.stack.imgur.com/9qAIN.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/9qAIN.jpg" alt="Nano SIM card"></a></p>

<p>Problem is, development board doesn't detect SIM card:</p>

<pre><code>at+cfun=1,1    
OK
at+cpin?    
+CME ERROR: SIM not inserted
at+csmins?    
+CSMINS: 0,0
</code></pre>

<p>This is the scenario: </p>

<ul>
<li>6 pin SIM in a 6 pin SIM card holder.</li>
<li>SIM works fine in a cel phone. Send/receive voice call/sms.</li>
<li>Older, working SIM from various providers doesn't get detected either.</li>
<li>Every other non-SIM related aspect works.</li>
<li>No reboots, no flickering.</li>
<li>Board takes care of regulating voltages and signal levels.</li>
</ul>

<p>I put an oscilloscope probe on the SIM_VDD pin (against board ground) and got this on every power-on:</p>

<p><a href="https://i.stack.imgur.com/DT358.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/DT358.jpg" alt="Sim VCC on startup"></a></p>

<p>Two 1.8v and two 3v pulses. That's all.</p>

<p>Please, note that I have no access to all SIM connexions (multi layer PCB).</p>

<p>How do I solve this problem?</p>
 -1: <p>The print on the PCB and product description at sellers site states it is GSM/GPRS board. The  module on the board comes from <a href="http://simcomm2m.com/En/" rel="nofollow noreferrer">SIMCom</a>. This particular <a href="http://simcomm2m.com/En/module/detail.aspx?id=138" rel="nofollow noreferrer">SIM800</a> module seems to have following capabilities as per SIMCom:</p>

<ul>
<li>Compliant to GSM phase 2/2+</li>
<li>GPRS multi-slot class 12/10</li>
<li>Quad-band 850/900/1800/1900MHz</li>
</ul>

<p>I think at the best you can only use a 2G SIM card on this board. Any 3G/4G SIM will not work.</p>

<p>Thanks for those images in the problem description, it gave me relevant keywords to search.</p>
