On Thu, 2 May 2024 16:05:45 +0200
Peter Rosin <peda@xxxxxxxxxx> wrote:
> 2024-05-02 at 15:49, Peter Rosin wrote:
> > Since you appear to need to change both the gpio pin and the io-channel, the
> > mux isn't a perfect fit. The closest you can get with the current code is to
> > create a gpio mux, I think. You would then use that mux twice to fan out both
> > io-channels, but only expose the "left leg" on the first fan-out and only the
> > "right leg" on the other. Something like this (untested, probably riddled with
> > errors, use salt etc etc):
> >
> > rcs: raw-current-sense {
> > compatible = "current-sense-shunt";
> > io-channels = <&adc 0>;
> > io-channel-name = "raw-current";
> > #io-channel-cells = <1>;
> >
> > shunt-resistor-micro-ohms = <3300000>;
> > };
> >
> > rvs: raw-voltage-sense {
> > compatible = "voltage-divider";
> > io-channels = <&adc 1>;
> > io-channel-name = "raw-voltage";
> > #io-channel-cells = <1>;
> >
> > output-ohms = <22>;
> > full-ohms = <222>;
> > };
> >
> > mux: gpio-mux {
> > compatible = "gpio-mux";
> > #mux-control-cells = <0>;
> >
> > gpios-mux = <&main_gpio0 29 GPIO_ACTIVE_HIGH>;
> > };
> >
> > current-sense {
> > compatible = "io-channel-mux";
> > io-channels = <&rcs 0>;
> > io-channel-names = "parent";
> >
> > mux-controls = <&mux>;
> >
> > channels = "current", "";
> > };
> >
> > voltage-sense {
> > compatible = "io-channel-mux";
> > io-channels = <&rvs 0>;
> > io-channel-names = "parent";
> >
> > mux-controls = <&mux>;
> >
> > channels = "", "voltage";
> > };
> >
> > What the mux solves is exclusion, so that the gpio pin is locked while
> > measurement is made on either current-sense or voltage-sense.
> >
> > However, the channels from the raw-{current,voltage}-sense nodes are exposed
> > to user space, and it will be possible to make "raw" measurements without
> > regard to how the gpio pin is set. That will of course not yield the desired
> > results, but is also a user error and might not be a big problem?
>
> I just realized that it's also possible to do this "the other way around". Maybe
> that makes more sense?
Ah, I'd failed to realize that this is about routing a single wire
through two different analog circuits that end on 'different' ADC inputs.
Pictures would help me out btw! Everyone loves ascii art.
Anyhow, I 'think' what you have here should work.
Jonathan
>
> Cheers,
> Peter
>
> mux: gpio-mux {
> compatible = "gpio-mux";
> #mux-control-cells = <0>;
>
> gpios-mux = <&main_gpio0 29 GPIO_ACTIVE_HIGH>;
> };
>
> rcs: raw-current-sense {
> compatible = "io-channel-mux";
> io-channels = <&adc 0>;
> io-channel-names = "parent";
> #io-channel-cells = <1>;
>
> mux-controls = <&mux>;
>
> channels = "raw-current", "";
> };
>
> rvs: raw-voltage-sense {
> compatible = "io-channel-mux";
> io-channels = <&adc 1>;
> io-channel-names = "parent";
> #io-channel-cells = <1>;
>
> mux-controls = <&mux>;
>
> channels = "", "raw-voltage";
> };
>
> current-sense {
> compatible = "current-sense-shunt";
> io-channels = <&rcs 0>;
> io-channel-name = "current";
>
> shunt-resistor-micro-ohms = <3300000>;
> };
>
> voltage-sense {
> compatible = "voltage-divider";
> io-channels = <&rvs 1>;
> io-channel-name = "voltage";
>
> output-ohms = <22>;
> full-ohms = <222>;
> };
>
> Cheers,
> Peter
