| Message ID | 064113a5-f8be-5b10-091f-a89b87baa5a3@xs4all.nl |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
| Series | [for,v4.15] dt-bindings/media/cec-gpio.txt: mention the CEC/HPD max voltages | expand |
On Sat, Dec 16, 2017 at 11:44:13AM +0100, Hans Verkuil wrote: > Mention the maximum voltages of the CEC and HPD lines. Since in the example > these lines are connected to a Raspberry Pi and the Rpi GPIO lines are 3.3V > it is a good idea to warn against directly connecting the HPD to the Raspberry > Pi's GPIO line. > > Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com> Reviewed-by: Rob Herring <robh@kernel.org> -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/Documentation/devicetree/bindings/media/cec-gpio.txt b/Documentation/devicetree/bindings/media/cec-gpio.txt index 46a0bac8b3b9..b36490aba7eb 100644 --- a/Documentation/devicetree/bindings/media/cec-gpio.txt +++ b/Documentation/devicetree/bindings/media/cec-gpio.txt @@ -4,6 +4,10 @@ The HDMI CEC GPIO module supports CEC implementations where the CEC line is hooked up to a pull-up GPIO line and - optionally - the HPD line is hooked up to another GPIO line. +Please note: the maximum voltage for the CEC line is 3.63V, for the HPD +line it is 5.3V. So you may need some sort of level conversion circuitry +when connecting them to a GPIO line. + Required properties: - compatible: value must be "cec-gpio". - cec-gpios: gpio that the CEC line is connected to. The line should be @@ -21,7 +25,7 @@ the following property is optional: Example for the Raspberry Pi 3 where the CEC line is connected to pin 26 aka BCM7 aka CE1 on the GPIO pin header and the HPD line is -connected to pin 11 aka BCM17: +connected to pin 11 aka BCM17 (some level shifter is needed for this!): #include <dt-bindings/gpio/gpio.h>
Mention the maximum voltages of the CEC and HPD lines. Since in the example these lines are connected to a Raspberry Pi and the Rpi GPIO lines are 3.3V it is a good idea to warn against directly connecting the HPD to the Raspberry Pi's GPIO line. Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com> --- -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html