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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 10:05:51 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 10:05:51 +0000
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treea94efe259b9009378be6d90eb30d2b019d95c194 /Documentation/devicetree/bindings/input/touchscreen/ti-tsc-adc.txt
parentInitial commit. (diff)
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Adding upstream version 5.10.209.upstream/5.10.209upstream
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+* TI - TSC ADC (Touschscreen and analog digital converter)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Required properties:
+- mfd
+ compatible: Should be
+ "ti,am3359-tscadc" for AM335x/AM437x SoCs
+ "ti,am654-tscadc", "ti,am3359-tscadc" for AM654 SoCs
+- child "tsc"
+ compatible: Should be "ti,am3359-tsc".
+ ti,wires: Wires refer to application modes i.e. 4/5/8 wire touchscreen
+ support on the platform.
+ ti,x-plate-resistance: X plate resistance
+ ti,coordinate-readouts: The sequencer supports a total of 16
+ programmable steps each step is used to
+ read a single coordinate. A single
+ readout is enough but multiple reads can
+ increase the quality.
+ A value of 5 means, 5 reads for X, 5 for
+ Y and 2 for Z (always). This utilises 12
+ of the 16 software steps available. The
+ remaining 4 can be used by the ADC.
+ ti,wire-config: Different boards could have a different order for
+ connecting wires on touchscreen. We need to provide an
+ 8 bit number where in the 1st four bits represent the
+ analog lines and the next 4 bits represent positive/
+ negative terminal on that input line. Notations to
+ represent the input lines and terminals resoectively
+ is as follows:
+ AIN0 = 0, AIN1 = 1 and so on till AIN7 = 7.
+ XP = 0, XN = 1, YP = 2, YN = 3.
+- child "adc"
+ compatible: Should be
+ "ti,am3359-adc" for AM335x/AM437x SoCs
+ "ti,am654-adc", "ti,am3359-adc" for AM654 SoCs
+ ti,adc-channels: List of analog inputs available for ADC.
+ AIN0 = 0, AIN1 = 1 and so on till AIN7 = 7.
+
+Optional properties:
+- child "tsc"
+ ti,charge-delay: Length of touch screen charge delay step in terms of
+ ADC clock cycles. Charge delay value should be large
+ in order to avoid false pen-up events. This value
+ effects the overall sampling speed, hence need to be
+ kept as low as possible, while avoiding false pen-up
+ event. Start from a lower value, say 0x400, and
+ increase value until false pen-up events are avoided.
+ The pen-up detection happens immediately after the
+ charge step, so this does in fact function as a
+ hardware knob for adjusting the amount of "settling
+ time".
+
+- child "adc"
+ ti,chan-step-opendelay: List of open delays for each channel of
+ ADC in the order of ti,adc-channels. The
+ value corresponds to the number of ADC
+ clock cycles to wait after applying the
+ step configuration registers and before
+ sending the start of ADC conversion.
+ Maximum value is 0x3FFFF.
+ ti,chan-step-sampledelay: List of sample delays for each channel
+ of ADC in the order of ti,adc-channels.
+ The value corresponds to the number of
+ ADC clock cycles to sample (to hold
+ start of conversion high).
+ Maximum value is 0xFF.
+ ti,chan-step-avg: Number of averages to be performed for each
+ channel of ADC. If average is 16 then input
+ is sampled 16 times and averaged to get more
+ accurate value. This increases the time taken
+ by ADC to generate a sample. Valid range is 0
+ average to 16 averages. Maximum value is 16.
+
+Example:
+ tscadc: tscadc@44e0d000 {
+ compatible = "ti,am3359-tscadc";
+ tsc {
+ ti,wires = <4>;
+ ti,x-plate-resistance = <200>;
+ ti,coordiante-readouts = <5>;
+ ti,wire-config = <0x00 0x11 0x22 0x33>;
+ ti,charge-delay = <0x400>;
+ };
+
+ adc {
+ ti,adc-channels = <4 5 6 7>;
+ ti,chan-step-opendelay = <0x098 0x3ffff 0x098 0x0>;
+ ti,chan-step-sampledelay = <0xff 0x0 0xf 0x0>;
+ ti,chan-step-avg = <16 2 4 8>;
+ };
+ }