mirror of
https://github.com/DCC-EX/CommandStation-EX.git
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d5a394d4e6
Update I2C addresses of HAL devices to type I2CAddress (to support extended address functions). Cast I2CAddress variables in DIAG calls to (int). Remove uses of max() function (not available on some platforms.
104 lines
3.8 KiB
C++
104 lines
3.8 KiB
C++
/*
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* © 2022 Paul M Antoine
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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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* The PCF8574 is a simple device; it only has one register. The device
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* input/output mode and pullup are configured through this, and the
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* output state is written and the input state read through it too.
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*
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* This is accomplished by having a weak resistor in series with the output,
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* and a read-back of the other end of the resistor. As an output, the
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* pin state is set to 1 or 0, and the output voltage goes to +5V or 0V
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* (through the weak resistor).
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*
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* In order to use the pin as an input, the output is written as
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* a '1' in order to pull up the resistor. Therefore the input will be
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* 1 unless the pin is pulled down externally, in which case it will be 0.
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*
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* As a consequence of this approach, it is not possible to use the device for
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* inputs without pullups.
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*/
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#ifndef IO_PCF8574_H
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#define IO_PCF8574_H
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#include "IO_GPIOBase.h"
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class PCF8574 : public GPIOBase<uint8_t> {
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public:
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static void create(VPIN firstVpin, uint8_t nPins, I2CAddress i2cAddress, int interruptPin=-1) {
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if (checkNoOverlap(firstVpin, nPins, i2cAddress)) new PCF8574(firstVpin, nPins, i2cAddress, interruptPin);
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}
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private:
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PCF8574(VPIN firstVpin, uint8_t nPins, I2CAddress i2cAddress, int interruptPin=-1)
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: GPIOBase<uint8_t>((FSH *)F("PCF8574"), firstVpin, nPins, i2cAddress, interruptPin)
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{
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requestBlock.setReadParams(_I2CAddress, inputBuffer, 1);
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}
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// The PCF8574 handles inputs by applying a weak pull-up when output is driven to '1'.
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// The pin state is driven '1' if the pin is an input, or if it is an output set to 1.
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// Unused pins are driven '0'.
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void _writeGpioPort() override {
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I2CManager.write(_I2CAddress, 1, (_portOutputState | ~_portMode) & _portInUse);
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}
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// The PCF8574 handles inputs by applying a weak pull-up when output is driven to '1'.
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// Therefore, writing '1' in _writePortModes is enough to set the module to input mode
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// and enable pull-up.
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void _writePullups() override { }
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void _writePortModes() override {
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_writeGpioPort();
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}
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// In immediate mode, _readGpioPort reads the device GPIO port and updates _portInputState accordingly.
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// When not in immediate mode, it initiates a request using the request block and returns.
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// When the request completes, _processCompletion finishes the operation.
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void _readGpioPort(bool immediate) override {
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if (immediate) {
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uint8_t buffer[1];
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I2CManager.read(_I2CAddress, buffer, 1);
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_portInputState = buffer[0] | _portMode;
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} else {
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requestBlock.wait(); // Wait for preceding operation to complete
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// Issue new request to read GPIO register
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I2CManager.queueRequest(&requestBlock);
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}
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}
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// This function is invoked when an I/O operation on the requestBlock completes.
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void _processCompletion(uint8_t status) override {
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if (status == I2C_STATUS_OK)
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_portInputState = inputBuffer[0] | _portMode;
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else
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_portInputState = 0xff;
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}
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// Set up device ports
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void _setupDevice() override {
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_writePortModes();
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}
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uint8_t inputBuffer[1];
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};
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#endif |