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* TI - TSC ADC (Touschscreen and analog digital converter)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Required properties:
- child "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"
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".
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>;
};
}
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