We experiencing a very strange behavior with a WISMO218 modem. It is controlled by an external uC. After powering up the modem and toggling the ON/OFF pin, the READY pin goes high. Exactly as described in the datsheet.
The problem is that 14 seconds after (give or take 1 second), the ready pin goes low irrespective of the uC sending AT commands or not.
We have isolated the problem to the SIM card. Without the card inserted, the modem READY pin remains high indefinitely although we are limited on the commands which the uC can send.
With the SIM card, the modem seems to power off automatically 14 seconds after the READY pin had gone high.
We also tried to get the phonebook directory, as well as making a call. In both cases, the modem replies with CMEE error value 100 (meaning “unknown”).
Did anybody experienced this before ? Any advice on what we can be doing wrong ? We know it is not the SIM card because we tried with cards, and the result is always the same.
Nelson Gon\c calves