[Letux-kernel] twl gpios / headset detect on gta04a5

H. Nikolaus Schaller hns at goldelico.com
Sun Sep 23 19:59:39 CEST 2018


> Am 23.09.2018 um 19:41 schrieb Andreas Kemnade <andreas at kemnade.info>:
> 
> On Sun, 23 Sep 2018 19:32:34 +0200
> "H. Nikolaus Schaller" <hns at goldelico.com> wrote:
> 
>> Hi,
>> 
>>> Am 23.09.2018 um 18:51 schrieb Andreas Kemnade <andreas at kemnade.info>:
>>> 
>>> Hi,
>>> 
>>> I am looking at the headset stuff.
>>> The detection is at gpio492 on gta04a5 if I
>>> understand everything right.
>>> I exported that and no reaction there on plugging
>>> And then I am wondering:
>>> root at gta04:/sys/class/gpio/gpio492# twl-i2c.sh GPIO r 0x13
>>> 0x00
>>> # twl-i2c.sh GPIO r 0x14
>>> 0x00
>>> 
>>> No pullups/downs enabled?!
>>> Hmm, floating inputs there?!
>>> 
>>> twl-i2c.sh GPIO w 0x13 0x20
>>> 
>>> does the trick. the exported gpio shows values.
>> 
>> Good finding!
>> 
>>> But are the pullup/down
>>> values correct there?
>> 
>> According to schematics:
>> 
>> 	http://projects.goldelico.com/p/gta04-main/downloads/48/
>> 
>> there is a 10k from the gpio to the switch and a 10k pull-down.
>> 
>> So there should be a pull-up for the gpio to provide energy.
> Well, that is one thing. I enabled the pullup using:
> 
> twl-i2c.sh GPIO w 0x13 0x20
> 
> More interesting are the *other* twl gpio pins. Floating stuff
> might be there. And therefore unecessary suspend currents.
> 
>> 
>> Then,
>> - if the headset is connected, the switch is open and the gpio should read "1"
>> - while a disconnected headset should connect the gpio to gnd through 20k which should be (note, this circuit has never been tested!) read as "0".
>> 
> That is wrong. It is tested be my now.

Wrong or not working?

> 
> Regards,
> Andreas
> 
> 
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