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https://github.com/DCC-EX/CommandStation-EX.git
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4f16a4ca06
Previously, pullups were enabled on GPIO Expander digital pins by default, even if the pin was only ever used as an output. This could lead to a spurious HIGH state being seen by external equipment before the output is initialised to LOW. To avoid this, the pin pullup is now not enabled until a configure or read operation is issued for the pin.
100 lines
3.3 KiB
C++
100 lines
3.3 KiB
C++
/*
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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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#ifndef IO_MCP23008_H
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#define IO_MCP23008_H
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#include "IO_GPIOBase.h"
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class MCP23008 : public GPIOBase<uint8_t> {
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public:
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static void create(VPIN firstVpin, uint8_t nPins, uint8_t I2CAddress, int interruptPin=-1) {
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new MCP23008(firstVpin, nPins, I2CAddress, interruptPin);
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}
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// Constructor
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MCP23008(VPIN firstVpin, uint8_t nPins, uint8_t I2CAddress, int interruptPin=-1)
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: GPIOBase<uint8_t>((FSH *)F("MCP23008"), firstVpin, min(nPins, 8), I2CAddress, interruptPin) {
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requestBlock.setRequestParams(_I2CAddress, inputBuffer, sizeof(inputBuffer),
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outputBuffer, sizeof(outputBuffer));
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outputBuffer[0] = REG_GPIO;
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}
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private:
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void _writeGpioPort() override {
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I2CManager.write(_I2CAddress, 2, REG_GPIO, _portOutputState);
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}
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void _writePullups() override {
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// Set pullups only for in-use pins. This prevents pullup being set for a pin that
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// is intended for use as an output but hasn't been written to yet.
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I2CManager.write(_I2CAddress, 2, REG_GPPU, _portPullup & _portInUse);
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}
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void _writePortModes() override {
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// Write 0 to IODIR for in-use pins that are outputs, 1 for others.
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uint8_t temp = ~(_portMode & _portInUse);
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I2CManager.write(_I2CAddress, 2, REG_IODIR, temp);
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// Enable interrupt-on-change for in-use pins that are inputs (_portMode=0)
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temp = ~_portMode & _portInUse;
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I2CManager.write(_I2CAddress, 2, REG_INTCON, 0x00);
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I2CManager.write(_I2CAddress, 2, REG_GPINTEN, temp);
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}
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void _readGpioPort(bool immediate) override {
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if (immediate) {
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uint8_t buffer;
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I2CManager.read(_I2CAddress, &buffer, 1, 1, REG_GPIO);
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_portInputState = buffer;
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} else {
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// Queue new request
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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];
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else
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_portInputState = 0xff;
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}
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void _setupDevice() override {
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// IOCON is set ODR=1 (open drain shared interrupt pin), INTPOL=0 (active-Low)
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I2CManager.write(_I2CAddress, 2, REG_IOCON, 0x04);
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_writePortModes();
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_writePullups();
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_writeGpioPort();
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}
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uint8_t inputBuffer[1];
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uint8_t outputBuffer[1];
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enum {
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// Register definitions for MCP23008
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REG_IODIR=0x00,
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REG_GPINTEN=0x02,
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REG_INTCON=0x04,
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REG_IOCON=0x05,
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REG_GPPU=0x06,
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REG_GPIO=0x09,
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};
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};
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#endif |