upm/src/mpr121/mpr121.cxx

/*
 * Author: Jon Trulson <jtrulson@ics.com>
 * Copyright (c) 2014 Intel Corporation.
 *
 * This program and the accompanying materials are made available under the
 * terms of the The MIT License which is available at
 * https://opensource.org/licenses/MIT.
 *
 * SPDX-License-Identifier: MIT
 */

#include <iostream>
#include <string>
#include <stdexcept>

#include "mpr121.hpp"

using namespace upm;
using namespace std;


MPR121::MPR121(int bus, uint8_t address) : m_i2c(bus)
{
  m_addr = address;
  mraa::Result ret = m_i2c.address(m_addr);

  if (ret != mraa::SUCCESS) 
    {
      throw std::invalid_argument(std::string(__FUNCTION__) +
                                  ": mraa_i2c_address() failed");
      return;
    }

  m_buttonStates = 0;
  m_overCurrentFault = false;
}

mraa::Result MPR121::writeBytes(uint8_t reg, uint8_t *buffer, int len)
{
  if (!len || !buffer)
    return mraa::SUCCESS;

  // create a buffer 1 byte larger than the supplied buffer,
  // store the register in the first byte
  uint8_t buf2[len + 1];

  buf2[0] = reg;

  // copy in the buffer after the reg byte
  for (int i=1; i<(len + 1); i++)
    buf2[i] = buffer[i-1];

  return m_i2c.write(buf2, len + 1);
}

int MPR121::readBytes(uint8_t reg, uint8_t *buffer, int len)
{
  if (!len || !buffer)
    return 0;

  // The usual m_i2c.read() does not work here, so we need to
  // read each byte individually.
  for (int i=0; i<len; i++)
    buffer[i] = m_i2c.readReg(reg + i);

  return len;
}

bool MPR121::configAN3944()
{
  // Configure the mpr121 chip as recommended in the AN3944 MPR121
  // Quick Start Guide

  mraa::Result rv;

  // First, turn off all electrodes by zeroing out the Electrode Configuration
  // register.
  // If this one fails, it's unlikely any of the others will succeed.
  uint8_t eleConf = 0x00;
  if ((rv = writeBytes(0x5e, &eleConf, 1)) != mraa::SUCCESS)
    {
      throw std::runtime_error(std::string(__FUNCTION__) +
                               ": writeBytes(0x5e) failed");
      return false;
    }

  // Section A
  // Filtering when data is greater than baseline
  // regs 0x2b-0x2e
  uint8_t sectA[] = { 0x01, 0x01, 0x00, 0x00 };
  if ((rv = writeBytes(0x2b, sectA, 4)) != mraa::SUCCESS)
    {
      throw std::runtime_error(std::string(__FUNCTION__) +
                               ": writeBytes(0x2b) failed");
      return false;
    }

  // Section B
  // Filtering when data is less than baseline
  // regs 0x2f-0x32
  uint8_t sectB[] = { 0x01, 0x01, 0xff, 0x02 };
  if ((rv = writeBytes(0x2f, sectB, 4)) != mraa::SUCCESS)
    {
      throw std::runtime_error(std::string(__FUNCTION__) +
                               ": writeBytes(0x2f) failed");
      return false;
    }

  // Section C
  // Touch Threshold/Release registers, ELE0-ELE11
  // regs 0x41-0x58
  //                __T_  __R_
  uint8_t sectC[] = { 0x0f, 0x0a,
                      0x0f, 0x0a,
                      0x0f, 0x0a,
                      0x0f, 0x0a,
                      0x0f, 0x0a,
                      0x0f, 0x0a,
                      0x0f, 0x0a,
                      0x0f, 0x0a,
                      0x0f, 0x0a,
                      0x0f, 0x0a,
                      0x0f, 0x0a,
                      0x0f, 0x0a };
  if ((rv = writeBytes(0x41, sectC, 24)) != mraa::SUCCESS)
    {
      throw std::runtime_error(std::string(__FUNCTION__) +
                               ": writeBytes(0x41) failed");
      return false;
    }

  // Section D
  // Filter configuration
  // reg 0x5d
  uint8_t filterConf = 0x24;
  if ((rv = writeBytes(0x5d, &filterConf, 1)) != mraa::SUCCESS)
    {
      throw std::runtime_error(std::string(__FUNCTION__) +
                               ": writeBytes(0x5d) failed");
      return false;
    }

  // Section F
  // Autoconfiguration registers
  // regs 0x7b-0x7f
  uint8_t sectF0 = 0x0b;
  if ((rv = writeBytes(0x7b, &sectF0, 1)) != mraa::SUCCESS)
    {
      throw std::runtime_error(std::string(__FUNCTION__) +
                               ": writeBytes(0x7b) failed");
      return false;
    }
  uint8_t sectF1[] = { 0x9c, 0x65, 0x8c };
  if ((rv = writeBytes(0x7d, sectF1, 3)) != mraa::SUCCESS)
    {
      throw std::runtime_error(std::string(__FUNCTION__) +
                               ": writeBytes(0x7d) failed");
      return false;
    }

  // Section E - this one must be set last, and switches to run mode
  // Enable all 12 electrodes, and set a pre-calibration to avoid
  // excessive calibration delay on startup.
  // reg 0x5e
  eleConf = 0x8c;
  if ((rv = writeBytes(0x5e, &eleConf, 1)) != mraa::SUCCESS)
    {
      throw std::runtime_error(std::string(__FUNCTION__) +
                               ": writeBytes(0x5e) failed");
      return false;
    }

  return true;
}

void MPR121::readButtons()
{
  uint8_t buffer[2];

  // read in the 2 bytes at register 0x00-0x01, and setup the member
  // variables accordingly.

  readBytes(0x00, buffer, 2);

  m_buttonStates = (buffer[0] | ((buffer[1] & 0x1f) << 8));
  if (buffer[1] & 0x80)
    m_overCurrentFault = true;
  else
    m_overCurrentFault = false;

  return;
}