Jinx wrote: >One command I do seem to have trouble with is the CNMI 1,1 to >activate the /RING0 line. Quite often it returns an error and needs >to be sent again. Other times it seems perfectly OK. And BTW, >AFAICT the hardware manual has the polarity of /RING0 wrong It should be active low, so that the RS-232 RI line pulses positive when a call is received. It's a good line to connect to an /INT pin, because it goes active not only when an incoming call is received but also just before an unsolicited result code is sent. Furthermore, I think it's possible to delay the sending of this code by keeping /RTS0 high while the host wakes up, and then driving it low when it is ready to process the serial data. This, together with the Cyclic Sleep modes, should make it possible to design a system which sleeps while waiting for an event and draws only a few mA in this mode (mostly for the GSM module which remains registered on the network but idle). I haven't yet tried out these last few features, though (I'm just going by the manual!) so there may be some nasty bugs awaiting me in a real implementation. As you say, it's enough of a job to work out how to use the basic GSM functions, let alone the arcane options. Most of the bugs that I have found have been in the newer MC45 module. The older TC35 seems relatively solid, although its firmware has now reached at least release 05.00 (what does that indicate?). I've checked my notes, and the MC45 bugs that I have found so far include: 1. AT^SM20=1^SSYNC=1 returns an ERROR, whereas AT^SSYNC=1^SM20=1 is OK. 2. ATV0 doesn't change all responses to numeric forms [fixed in V02.04] 3. If signal strength is low, module gives up hunting for a GSM network and returns +CREG: 0,3 (registration denied) instead of continuing indefinitely with +CREG: 0,2 (searching). [fixed in V02.04] 4. Some AT commands on the same line as AT&F are ignored. For example, AT&FV0 doesn't switch to numeric responses. Work-around: send AT&F on its own. 5. ATS0=0 returns an ERROR response if no SIM card is inserted. This is usually an error condition but, oddly, ATS0? returns a response of "000" and OK. I hope this helps. All the best. -- Ian Chapman Chapmip Technology, UK -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.