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Create IO_LedChain.h
Shift register output device.
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Neil McKechnie
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IO_LedChain.h
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256
IO_LedChain.h
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/*
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* © 2021, Neil McKechnie. All rights reserved.
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*
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* This file is part of DCC++EX API
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*
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* This is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* It is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with CommandStation. If not, see <https://www.gnu.org/licenses/>.
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*/
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/*
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* This driver is designed for the LED Driver devices which are characteristically
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* driven with DATAIN, CLOCK and LATCH signals, and chained one to another by connecting
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* the DATAOUT pin of one device to the next device's DATAIN pin. The devices act like a
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* shift register, so the data bits are sent to the first device's DATAIN pin and clocked through
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* the shift register (bit by bit). Once the shift register is loaded, the data is latched
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* into the devices when the LATCH signal is pulsed.
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*
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* Some devices drive on/off outputs, so one bit is written to the shift register for each
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* output to be driven. For example, with 16 x 1-bit device, 16 bits are sent, one for each
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* LED output.
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*
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* Other devices allow the outputs to be driven by grey-scale, with up to 16 bit resolution.
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* In this case, the number of bits sent to the shift register increases drastically; for
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* 12 LEDs at 16-bit resolution, a total of 172 bits must be sent for each device in the chain.
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* for 24 LEDs at 12-bit resolution, 268 bits must be sent for each device.
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* The most significant bit of each value is sent first.
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*
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* RGB LEDs may be driven by connecting an output to each of the R/G/B wires of the LED, but
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* most of the driver devices sink current to ground through the LED, so an RGB LED with a
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* common anode (+ve terminal) must be used with these devices. Check the datasheet for details.
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*
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* Device variants known:
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* TLC5947: 24 x 12-bit
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* TLC5940: 16 x 12-bit
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* TLC6C598: 8 x 1-bit
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* TLC6C5912: 12 x 1-bit
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* STP24DP05: 8 x 3-bit (RGB)
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* MAX6979: 16 x 1-bit
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* 74HC595: 8 x 1-bit
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*
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* All of these devices are able to support clock pulses of 30ns or shorter with a clock rate of
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* 10MHz or faster; however, the Arduino isn't capable of running this fast, and the shortest pulse
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* length that is generated is 750ns, and a peak clock rate of 186kHz. Faster rates could be
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* achieved by using the SPI interface, but if any other SPI device is in use then additional
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* device select circuitry would be required.
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*
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*/
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#ifndef IO_LEDCHAIN_H
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#define IO_LEDCHAIN_H
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#include "IODevice.h"
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class LedChain : public IODevice {
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private:
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#ifdef ARDUINO_ARCH_AVR
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class DigPin {
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private:
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volatile uint8_t *ptr;
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uint8_t mask;
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public:
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DigPin() { ptr = &mask; }
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DigPin(int pinNumber) {
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if (pinNumber >= 0 && pinNumber <= NUM_DIGITAL_PINS) {
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int port = digitalPinToPort(pinNumber);
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if (port != NOT_A_PORT) {
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pinMode(pinNumber, OUTPUT);
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mask = digitalPinToBitMask(pinNumber);
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ptr = portOutputRegister(port);
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return;
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}
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}
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// Pin not valid, set pointer to somewhere benign
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ptr = &mask;
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}
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void setValue(bool value) {
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noInterrupts();
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if (value)
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*ptr |= mask;
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else
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*ptr &= ~mask;
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interrupts();
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}
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void pulse() {
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noInterrupts();
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*ptr |= mask;
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*ptr &= ~mask;
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interrupts();
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}
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};
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#else
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// Fall back to digitalWrite calls.
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class DigPin {
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private:
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int _pinNumber = 0;
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public:
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DigPin() {};
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DigPin(int pinNumber) {
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pinMode(pinNumber, OUTPUT);
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_pinNumber = pinNumber;
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}
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void setValue(bool value) {
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digitalWrite(_pinNumber, value);
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}
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void pulse() {
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digitalWrite(_pinNumber, 1);
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digitalWrite(_pinNumber, 0);
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}
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};
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#endif
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// pins must be arduino GPIO pins, not extender pins or HAL pins.
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DigPin _dataPin;
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DigPin _clockPin;
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DigPin _latchPin;
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int _bitsPerPin = 0;
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byte *_values;
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bool _changed = true;
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int _nextRegisterPin = 0;
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unsigned long _lastEntryTime = 0;
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public:
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// Constructor performs static initialisation of the device object
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LedChain (VPIN vpin, int nPins, int dataPin, int clockPin, int latchPin, int bitsPerPin=1) {
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_firstVpin = vpin;
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_nPins = nPins;
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_dataPin = DigPin(dataPin);
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_clockPin = DigPin(clockPin);
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_latchPin = DigPin(latchPin);
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_bitsPerPin = bitsPerPin;
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if (_bitsPerPin == 1)
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_values = (byte *)calloc((_nPins+7)/8, 1); // 1 byte per 8 pins (rounded up)
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else
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_values = (byte *)calloc(_nPins, 2); // 2 bytes per pin.
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addDevice(this);
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}
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// Static create function provides alternative way to create object
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static void create(VPIN vpin, int nPins, int dataPin, int clockPin, int latchPin, int bitsPerPin=1) {
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new LedChain (vpin, nPins, dataPin, clockPin, latchPin, bitsPerPin);
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}
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protected:
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// _begin function called to perform dynamic initialisation of the device
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void _begin() override {
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_dataPin.setValue(0);
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_clockPin.setValue(0);
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_latchPin.setValue(0);
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#if defined(DIAG_IO)
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_display();
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#endif
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}
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// Digital write - write on or off.
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void _write(VPIN vpin, int value) {
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if (_bitsPerPin == 1) {
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int pin = vpin - _firstVpin;
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uint8_t *ptr = _values + pin/8;
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uint8_t mask = 1 << (pin % 8);
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if (value)
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*ptr |= mask;
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else
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*ptr &= ~mask;
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} else {
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// Write maximum positive value (will be truncated if too large)
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writeAnalogue(vpin, value ? 0x7fff : 0);
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}
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_changed = true;
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}
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// Analogue write - write the supplied value
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void _writeAnalogue(VPIN vpin, int value) {
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if (_bitsPerPin == 1 ) {
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_write(vpin, value);
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} else {
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int pin = vpin - _firstVpin;
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uint16_t *ptr = (uint16_t *)(_values + pin*2);
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*ptr = value;
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}
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_changed = true;
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}
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// _loop function - refresh device every 100ms if anything has changed.
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void _loop(unsigned long currentMicros) override {
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int count = 0;
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if (_changed) {
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// Remember the time that this output cycle started.
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if (_nextRegisterPin == 0) _lastEntryTime = currentMicros;
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if (_bitsPerPin == 1) {
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int pin=_nextRegisterPin;
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uint8_t *ptr = _values + pin/8;
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uint8_t mask = 1;
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while (true) {
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// For each pin, write one bit to the shift register
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uint8_t value = (*ptr & mask) ? 1 : 0;
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_dataPin.setValue(value);
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_clockPin.pulse();
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mask <<= 1;
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if (mask == 0) {
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if (++count >= 2) { // max of 16 pins per loop entry
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_nextRegisterPin = pin;
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return; // Resume on next loop entry
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}
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// Move to next byte
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ptr++;
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mask = 1;
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}
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if (++pin >= _nPins) break;
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}
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} else {
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// Multiple bits per pin - up to 16 bits stored in two bytes.
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int pin=_nextRegisterPin;
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uint16_t *ptr = (uint16_t *)_values + pin;
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while (true) {
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uint16_t value = *ptr++;
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// For each pin, write the requisite number of bits to the shift register
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uint16_t mask = 1 << (_bitsPerPin-1);
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while (mask) {
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_dataPin.setValue((value & mask) ? 1 : 0);
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_clockPin.pulse();
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mask >>= 1;
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}
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if (++pin >= _nPins) break; // finished.
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if (++count >= 1) { // max of 1 pin per loop entry
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_nextRegisterPin = pin;
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return; // Resume on next loop entry
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}
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}
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}
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// Pulse latch pin to transfer data from shift register to outputs.
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_latchPin.pulse();
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//_changed = false;
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}
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_nextRegisterPin = 0; // Restart from the beginning on next entry
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delayUntil(_lastEntryTime+100000UL); // At most one update cycle per 100ms
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}
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void _display() override {
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DIAG(F("LedChain Configured on Vpins:%d-%d DataPin:%d ClockPin:%d LatchPin:%d BitsPerOutput:%d"),
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_firstVpin, _firstVpin+_nPins-1, _dataPin, _clockPin, _latchPin, _bitsPerPin);
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}
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};
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#endif //IO_LEDCHAIN_H
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