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IO_TouchKeypad.h
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IO_TouchKeypad.h
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/*
* © 2023, Neil McKechnie. All rights reserved.
*
* This file is part of DCC++EX API
*
* This is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* It is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with CommandStation. If not, see <https://www.gnu.org/licenses/>.
*/
/*
* Driver for capacitative touch-pad based on the TTP229-B chip with serial
* (not I2C) output. The touchpad has 16 separate pads in a 4x4 matrix,
* numbered 1-16. The communications with the pad are via a clock signal sent
* from the controller to the device, and a data signal sent back by the device.
* The pins clockPin and dataPin must be local pins, not external (GPIO Expander)
* pins.
*
* To use,
* TouchKeypad::create(firstVpin, 16, clockPin, dataPin);
*
* NOTE: Most of these keypads ship with only 8 pads enabled. To enable all
* sixteen pads, locate the area of the board labelled P1 (four pairs of
* holes labelled 1 to 4 from the left); solder a jumper link between the pair
* labelled 3 (connected to pin TP2 on the chip). When this link is connected,
* the pins OUT1 to OUT8 are not used but all sixteen touch pads are operational.
*
* TODO: Allow a list of datapins to be provided so that multiple keypads can
* be read simultaneously by the one device driver and the one shared clock signal.
* As it stands, we can configure multiple driver instances, one for each keypad,
* and it will work fine. The clock will be driven to all devices but only one
* driver will be reading the responses from its corresponding device at a time.
*/
#ifndef IO_TOUCHKEYPAD_H
#define IO_TOUCHKEYPAD_H
#include "IODevice.h"
class TouchKeypad : public IODevice {
private:
// Here we define the device-specific variables.
uint16_t _inputStates = 0;
VPIN _clockPin;
VPIN _dataPin;
public:
// Static function to handle create calls.
static void create(VPIN firstVpin, int nPins, VPIN clockPin, VPIN dataPin) {
if (checkNoOverlap(firstVpin,nPins)) new TouchKeypad(firstVpin, nPins, clockPin, dataPin);
}
protected:
// Constructor.
TouchKeypad(VPIN firstVpin, int nPins, VPIN clockPin, VPIN dataPin) {
_firstVpin = firstVpin;
_nPins = (nPins > 16) ? 16 : nPins; // Maximum of 16 pads per device
_clockPin = clockPin;
_dataPin = dataPin;
addDevice(this);
}
// Device-specific initialisation
void _begin() override {
#if defined(DIAG_IO)
_display();
#endif
// Set clock pin as output, initially high, and data pin as input.
// Enable pullup on the input so that the default (not connected) state is
// 'keypad not pressed'.
ArduinoPins::fastWriteDigital(_clockPin, 1);
pinMode(_clockPin, OUTPUT);
pinMode(_dataPin, INPUT_PULLUP); // Force defined state when no connection
}
// Device-specific read function.
int _read(VPIN vpin) {
if (vpin < _firstVpin || vpin >= _firstVpin + _nPins) return 0;
// Return a value for the specified vpin.
return _inputStates & (1<<(vpin-_firstVpin)) ? 1 : 0;
}
// Loop function to do background scanning of the keyboard.
// The TTP229 device requires clock pulses to be sent to it,
// and the data bits can be read on the rising edge of the clock.
// By default the clock and data are inverted (active-low).
// A gap of more than 2ms is advised between successive read
// cycles, we wait for 100ms between reads of the keyboard as this
// provide a good enough response time.
// Maximum clock frequency is 512kHz, so put a 1us delay
// between clock transitions.
//
void _loop(unsigned long currentMicros) {
// Clock 16 bits from the device
uint16_t data = 0, maskBit = 0x01;
for (uint8_t pad=0; pad<16; pad++) {
ArduinoPins::fastWriteDigital(_clockPin, 0);
delayMicroseconds(1);
ArduinoPins::fastWriteDigital(_clockPin, 1);
data |= (ArduinoPins::fastReadDigital(_dataPin) ? 0 : maskBit);
maskBit <<= 1;
delayMicroseconds(1);
}
_inputStates = data;
#ifdef DIAG_IO
static uint16_t lastData = 0;
if (data != lastData) DIAG(F("KeyPad: %x"), data);
lastData = data;
#endif
delayUntil(currentMicros + 100000); // read every 100ms
}
// Display information about the device, and perhaps its current condition (e.g. active, disabled etc).
void _display() {
DIAG(F("TouchKeypad Configured on Vpins:%u-%u SCL=%d SDO=%d"), (int)_firstVpin,
(int)_firstVpin+_nPins-1, _clockPin, _dataPin);
}
};
#endif // IO_TOUCHKEYPAD_H