[also Cc: IIO and devicetree maintainers]
On Wed, May 01, 2024 at 08:38:53PM -0300, João Paulo Gonçalves wrote:
> Hello all,
>
> We need to support a hardware that can measure current and voltage on
> the same differential analog input, similar to a multimeter. The mode
> of measurement is controlled by a GPIO switch and goes to different
> ADC inputs depending on the mode. If the switch is enabled, a current
> loop with a shunt is enabled for current measurement; otherwise, voltage
> is measured. From the software point of view, we are considering using
> the iio-rescale driver as a consumer of an ADC IIO parent device. One
> of the problems is that we need to change the mode of measurement at
> runtime, but we are trying to avoid using some userspace "hack". The
> other is that for a minimal solution to enable the mode from boot, we
> can use a gpio-hog and control it with overlays. However,
> still would be better that this was done by the kernel. Do you know
> or have some guidance on how to properly support this in the kernel?
>
> For the in kernel gpio solution, this is a draft of DT we are thinking:
>
> current-sense {
> compatible = "current-sense-shunt";
> io-channels = <&adc 0>;
> gpio = <&main_gpio0 29 GPIO_ACTIVE_HIGH>;
> shunt-resistor-micro-ohms = <3300000>;
> };
>
> voltage-sense {
> compatible = "voltage-divider";
> io-channels = <&adc 1>;
> gpio = <&main_gpio0 29 GPIO_ACTIVE_LOW>;
> output-ohms = <22>;
> full-ohms = <222>;
> };
What are these ohms and where do you get them?
Confused...
--
An old man doll... just what I always wanted! - Clara
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