[Ovmsdev] sprintf / crashes

Michael Balzer dexter at expeedo.de
Mon Dec 31 23:23:59 HKT 2012


I think I found my link dropping problem: scanning a diag log I took, I 
found out CIPSEND will fail with a plain "ERROR" if the data size 
exceeds about 1500 bytes. I guess that's either the SIM908 buffer size 
or the max network packet size. I thought the SIM908 would handle 
dividing data into packets as needed. The SIM908 manual mentions the max 
packet size depends on network status and should be queried by 
"AT+CIPSEND?". After the overrun net_state_activity() will not recognize 
"ERROR" to terminate the pending msg, so will run into the timeout and 
start a network re-init.

My battery status data exceeds 1500 bytes on first run and later on if 
enough cells need updates. I'll think about how to split up data packets 
into multiple CIPSENDs. Would be nice if the net functions take care of 
this transparently.

A secondary issue turned up from the diag log: the SIM908 crashed in the 
middle of a CIPSEND command while the module continued to run normally. 
The module still thought it's in NET_STATE_READY, so did not 
re-initalize the modem. The connection could then be established on the 
next CIPSTART, but the complete INIT stuff had not been done. So it 
seems independant SIM908 resets need to be handled as well, and they can 
occur anytime. I'll see if I can solve that too.


Am 30.12.2012 15:42, schrieb Michael Balzer:
> I hesitate to merge into the master because I currently have link / 
> connectivity problems, especially during driving. I introduced a GPS 
> logging to optimize my antenna positions and managed to get some 
> really nice tracks three days ago, so I don't think this is related to 
> my changes... but I'm not 100% sure. I tried different antenna 
> positions and another GSM network, but the connection keeps dropping 
> when moving the car, and GPS position updates need minutes. Could be 
> weather conditions ...or some tricky race condition bug?

Michael Balzer * Paradestr. 8 * D-42107 Wuppertal
Fon 0202 / 272 2201 * Handy 0176 / 206 989 26

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