Create IO_TouchKeypad.h

Driver for 16-pad capacitative key pad device (TTP229-B based).
2024-12-23 12:51:24 +01:00 · 2023-03-02 23:01:44 +00:00 · 2023-03-02 23:01:44 +00:00 · 19bbb186e7
commit 19bbb186e7
parent ca4592dc3e
1 changed files with 134 additions and 0 deletions
--- a/IO_TouchKeypad.h
+++ b/IO_TouchKeypad.h
@ -0,0 +1,134 @@
+/*
+ *  © 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:%d-%d SCL=%d SDO=%d"), (int)_firstVpin, 
+      (int)_firstVpin+_nPins-1, _clockPin, _dataPin);
+  }
+
+
+};
+
+#endif // IO_TOUCHKEYPAD_H