On the M590 exist 10 pin = I pin. when exist incoming Call or SMS on this pin is LOW level for 30ms AND in SERIAL it transmit "RING".
so my module is worked as expected 2 weeks. today I switch it ON for further testing and observe that no "RING" in SERIAL when SMS is received. Firstly I thought that no RING in serial only and exist LOW level. but after experiment I notice that when CALL is received LOW level is exist, BUT when SMS is received LOW level is not exist.
So when SMS is received, no RING in SERIAl and no LOW level on pin 10
who know how to fix this ?
may be I can update firmware ? is it possible? or exist other solution?