xref: /openbmc/linux/Documentation/devicetree/bindings/input/touchscreen/ti,am3359-tsc.yaml (revision 8c4838a8)

# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
%YAML 1.2
---
$id: http://devicetree.org/schemas/input/touchscreen/ti,am3359-tsc.yaml#
$schema: http://devicetree.org/meta-schemas/core.yaml#

title: TI AM3359 Touchscreen controller

maintainers:
  - Miquel Raynal <miquel.raynal@bootlin.com>

properties:
  compatible:
    const: ti,am3359-tsc

  ti,wires:
    description: Wires refer to application modes i.e. 4/5/8 wire touchscreen
      support on the platform.
    $ref: /schemas/types.yaml#/definitions/uint32
    enum: [4, 5, 8]

  ti,x-plate-resistance:
    description: X plate resistance
    $ref: /schemas/types.yaml#/definitions/uint32

  ti,coordinate-readouts:
    description: 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.
    $ref: /schemas/types.yaml#/definitions/uint32
    minimum: 1
    maximum: 6

  ti,wire-config:
    description: Different boards could have a different order for connecting
      wires on touchscreen. We need to provide an 8-bit number where the
      first 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 respectively are as follows, AIN0 = 0, AIN1 = 1
      and so on until AIN7 = 7. XP = 0, XN = 1, YP = 2, YN = 3.
    $ref: /schemas/types.yaml#/definitions/uint32-array
    minItems: 4
    maxItems: 8

  ti,charge-delay:
    description: 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".
    $ref: /schemas/types.yaml#/definitions/uint32

required:
  - compatible
  - ti,wires
  - ti,x-plate-resistance
  - ti,coordinate-readouts
  - ti,wire-config

additionalProperties: false

examples:
  - |
    tsc {
        compatible = "ti,am3359-tsc";
        ti,wires = <4>;
        ti,x-plate-resistance = <200>;
        ti,coordinate-readouts = <5>;
        ti,wire-config = <0x00 0x11 0x22 0x33>;
        ti,charge-delay = <0x400>;
    };