Hi Jacek,
On Wed, Sep 9, 2015 at 9:25 AM, Jacek Anaszewski
<[email protected]> wrote:
> On 09/08/2015 04:37 PM, Linus Walleij wrote:
>> On Tue, Sep 8, 2015 at 12:51 PM, Jacek Anaszewski
>> <[email protected]> wrote:
>>> On 09/07/2015 03:22 PM, Geert Uytterhoeven wrote:
>>>> Something like this?
>>>>
>>>> VCC VCC
>>>> | |
>>>> R R
>>>> | |
>>>> __|__ | |
>>>> +---o o---+ _|_
>>>> | | \ /
>>>> | | ---
>>>> GND R |
>>>> | |
>>>> | |-+
>>>> | |<+
>>>> GPIO -----------------+---------|-|
>>>> |
>>>> |
>>>> GND
>>>
>>> You would need also resistor to avoid short-circuit
>>> when the switch is on.
>>
>> There is a resistor AFAICT.
>
> Indeed. For some reason my mind filtered out these 'R'
> characters.
Sorry for the bad drawing, which is a simplified extract from the real
schematic diagram.
>> But consider the GPIO side which is opaque
>> here. When used as input it is often high impedance
>> but when used to drive it is not.
>>
>> Doesn't this mean the output actually has to be
>> open collector (open drain)?
I think the GPIO is just a standard push-pull output in output mode.
> I think that GPIO control register would have to be
> altered to switch between particular modes.
>
> Let's analyze possible modes, assuming that the transistor
> is a bipolar PNP:
Actually it's an N-channel MOSFET.
>>> We'd have to ask Linus if he welcomes drivers for this type
>>> of home-made circuits in mainline. If yes, then probably someone would
>>> have to build the circuit, develop and test the driver on it, and
>>> finally come up with a detailed documentation.
>>> Are you the volunteer? :)
>>
>> Of course he's considering it or he wouldn't write :)
This is not a home-made circuit.
Let's see how it goes when the hardware arrives...
Thanks, now I know no driver exists yet.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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