Add an option to suppress the echo of modem.

In addition to the echo suppress, The following changes are also
1) use readlines() instead of readline() to avoid some
buffered data like: ['\r\n', '+CEREG: 2\r\n', '\r\n', '+CEREG: 0\r\n']

2) Option disable_operation will put modem into a mode more silent.

3) Changing the logging level to extract more verbose information as we
still in the stage to understand the modem behavior.

TEST=Manually with

Change-Id: I5705d441a35a791b78d2d7998f6e2379ca5f444c
Reviewed-by: Cheng-Yi Chiang <>
Commit-Queue: Chun-Ta Lin <>
Tested-by: Chun-Ta Lin <>
1 file changed