title: logging onto the GPRS APN using sim900 in an embedded situation with no operating system
body: <p>I am using an embedded microprocessor to communicate with a SIM900 GPRS modem. The sim900 has an embedded tcp/ip stack but no embedded PPP stack, and my embedded environment has neither of these stacks.</p>
  
  <p>With other devices I have followed these steps:</p>
  
  <ol>
  <li>at+cgdcont="IP","internet",,</li>
  <li>atd*99***1#</li>
  <li>called a PPP function that took take care of the login to the APN (and presumably the authentication &amp; LCP etc).</li>
  <li>called a TCP function that connected to the remote server.</li>
  </ol>
  
  <p>But now I have to do the PPP part myself. so I am at a loss locating all the necessary information.... can anyone point me in the right direction?</p>
  
  <p>when I use hyperterm so as to see what happens with <code>ATD*99***1#</code> it connects and returns a lot of PPP frames which i suppose i have to write a module to deal with. But I did notice, on a number of sites, that the login to the APN is not mentioned at all, so is there a way of bypassing the login?</p>
  
  <p>When I follow the example in the SIM900 docs, I get an error indicating (quite rightly) that the PDP is deactivated...</p>