I have now finally got an aerial connection to my GSM modem, and it seems that the
transmission causes the 7260 to reset - about every 20 seconds!
Setup: 7260, Modem-2 daughterboard, Multitech GSM/GPRS socket modem,
900/1800MHz.
With the SIM inserted and an aerial plugged in, the 7260 resets itself about every 20
seconds. There is nothing logged to the console on /dev/ttyAM0 apart from the startup
messages.
If I unplug the aerial OR remove the SIM it doesn't happen. It can't be a software problem
as the modem is simply seen as a serial device, /dev/tts/3. There's no software running
that interacts with the serial port when it resets.
I have another system, a 7250, plugged into the same 12V power supply which runs
perfectly, so it's not off-board power supply. The voltage at the power pin to the modem
is 5.00 V, so it's probably not on board power sagging too low.
Interestingly, although it's a 5V modem, I initially plugged it in at 3.3V, and it seemed to
work except it could not access the SIM.
I am suspecting the radio transmision is causing the CPU to reset, but I don't know what to
do about it.
This 7260 is not in its enclosure, but sitting bare on the bench. However, the 7250 is
about the same distance from the aerial and is not affected. Putting the 7260 into its
enclosure does not change things; it still resets and the 7250 (not enclosed) doesn't.
I assume *someone*
has used a GSM modem with a 7250/7260 before?
Martin