GSM modem power on/off issues at gta01

Andy Powell openmoko at
Fri Feb 29 09:27:50 CET 2008

On Friday 29 February 2008 04:24, Sean Chiang wrote:
> HI! list,
> Here's my recent observation about the power management of GSM modem
> within gta01,
> just a note. If we want to power off GSM modem _completely_ we need to
> issue AT at POFF
> to modem and subsequently echo "0" > power_on.
> Without AT at POFF, even shutdown the gta01 the battery life still be
> consumed by GSM modem.
> My misunderstanding is the GSM modem could be power on/down only one
> time, after you power
> off GSM modem, you couldn't power on modem anymore. And I'm wrong, the
> modem could be
> powered on|off by echo "1"|"0" > power_on repeatedly.
> A wrapper called gsm-pm which is called by init when device on, is used
> to control the on/off GSM modem. gsm-pm will
> power on modem then run gsmd. After that, gsm-pm will wait until gsmd is
> killed. When gsm-pm detect the gsmd
> was killed it will send "AT at POFF" to modem then echo "0" to power_on.
> With this we doesn't need to worry the gsmd is dead or not. I tried to
> write the gsm-pm, could be download from
>  I still have
> problem when write AT at POFF to modem.
> Is this idea ok?
> -Sean Chiang

I don't mean to criticize but shouldn't  we be using snprintf and not 
sprintf ?


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