Patriot Geek: ATOM Matrix: Grove IR Remote Module

The goal of this post and the next post is to reverse engineer the IR signals sent by a DVD remote control. We will use the Grove IR Remote module to read the signals that correspond to a few select buttons. The project will be completed in the next post.

While all of the code here is not specific to the ATOM Matrix, the IR codes transmitted by the remote control are HIGHLY specific to the particular remote!

IR Remote Module

The Grove IR Remote module is different from the PIR or potentiometer modules in that the IR Remote performs both output and input - it can both emit (pin 32) and receive (pin 26) IR signals.

First, here is a simple app that flashes the IR LED on the Remote. In order to see it, use either a computer's webcam, or the camera on an older phone.

/*
 * Grove-IR-Remote-01.ino
 * 
 * By: Mike Klepper
 * Date: 26 April 2020
 * 
 * Demonstrates how to turn on/off the IR LED on the IR Remote
 */

#include "M5Atom.h"

int outputPin = 26;

void setup() 
{
  M5.begin(true, false, true);
  delay(20);
  pinMode(outputPin, OUTPUT);
}

void loop() 
{
  digitalWrite(outputPin, HIGH);
  delay(500);
  M5.update();

  digitalWrite(outputPin, LOW);
  delay(500);
  M5.update();
}

Application: Grove-IR-Remote-02 (Same as IRrecvDumpV2)

To read IR signals, first install the "IRremoteESP8266" library using the Library Manager - it works with the ESP32 as well. One of the example sketches is called IRrecvDumpV2, reproduced as-is with comments and all, except that kRecvPin has been set to 32.

#include "M5Atom.h"

#include <IRrecv.h>
#include <IRremoteESP8266.h>
#include <IRac.h>
#include <IRtext.h>
#include <IRutils.h>

// ==================== start of TUNEABLE PARAMETERS ====================
// An IR detector/demodulator is connected to GPIO pin 14
// e.g. D5 on a NodeMCU board.
// Note: GPIO 16 won't work on the ESP8266 as it does not have interrupts.
const uint16_t kRecvPin = 32;

// The Serial connection baud rate.
// i.e. Status message will be sent to the PC at this baud rate.
// Try to avoid slow speeds like 9600, as you will miss messages and
// cause other problems. 115200 (or faster) is recommended.
// NOTE: Make sure you set your Serial Monitor to the same speed.
const uint32_t kBaudRate = 115200;

// As this program is a special purpose capture/decoder, let us use a larger
// than normal buffer so we can handle Air Conditioner remote codes.
const uint16_t kCaptureBufferSize = 1024;

// kTimeout is the Nr. of milli-Seconds of no-more-data before we consider a
// message ended.
// This parameter is an interesting trade-off. The longer the timeout, the more
// complex a message it can capture. e.g. Some device protocols will send
// multiple message packets in quick succession, like Air Conditioner remotes.
// Air Coniditioner protocols often have a considerable gap (20-40+ms) between
// packets.
// The downside of a large timeout value is a lot of less complex protocols
// send multiple messages when the remote's button is held down. The gap between
// them is often also around 20+ms. This can result in the raw data be 2-3+
// times larger than needed as it has captured 2-3+ messages in a single
// capture. Setting a low timeout value can resolve this.
// So, choosing the best kTimeout value for your use particular case is
// quite nuanced. Good luck and happy hunting.
// NOTE: Don't exceed kMaxTimeoutMs. Typically 130ms.
#if DECODE_AC
// Some A/C units have gaps in their protocols of ~40ms. e.g. Kelvinator
// A value this large may swallow repeats of some protocols
const uint8_t kTimeout = 50;
#else   // DECODE_AC
// Suits most messages, while not swallowing many repeats.
const uint8_t kTimeout = 15;
#endif  // DECODE_AC
// Alternatives:
// const uint8_t kTimeout = 90;
// Suits messages with big gaps like XMP-1 & some aircon units, but can
// accidentally swallow repeated messages in the rawData[] output.
//
// const uint8_t kTimeout = kMaxTimeoutMs;
// This will set it to our currently allowed maximum.
// Values this high are problematic because it is roughly the typical boundary
// where most messages repeat.
// e.g. It will stop decoding a message and start sending it to serial at
//      precisely the time when the next message is likely to be transmitted,
//      and may miss it.

// Set the smallest sized "UNKNOWN" message packets we actually care about.
// This value helps reduce the false-positive detection rate of IR background
// noise as real messages. The chances of background IR noise getting detected
// as a message increases with the length of the kTimeout value. (See above)
// The downside of setting this message too large is you can miss some valid
// short messages for protocols that this library doesn't yet decode.
//
// Set higher if you get lots of random short UNKNOWN messages when nothing
// should be sending a message.
// Set lower if you are sure your setup is working, but it doesn't see messages
// from your device. (e.g. Other IR remotes work.)
// NOTE: Set this value very high to effectively turn off UNKNOWN detection.
const uint16_t kMinUnknownSize = 12;

// Legacy (No longer supported!)
//
// Change to `true` if you miss/need the old "Raw Timing[]" display.
#define LEGACY_TIMING_INFO false
// ==================== end of TUNEABLE PARAMETERS ====================

// Use turn on the save buffer feature for more complete capture coverage.
IRrecv irrecv(kRecvPin, kCaptureBufferSize, kTimeout, true);
decode_results results;  // Somewhere to store the results

// This section of code runs only once at start-up.
void setup() {
M5.begin(true, false, true);
  delay(10);
  
#if defined(ESP8266)
  Serial.begin(kBaudRate, SERIAL_8N1, SERIAL_TX_ONLY);
#else  // ESP8266
  Serial.begin(kBaudRate, SERIAL_8N1);
#endif  // ESP8266
  while (!Serial)  // Wait for the serial connection to be establised.
    delay(50);
  Serial.printf("\n" D_STR_IRRECVDUMP_STARTUP "\n", kRecvPin);
#if DECODE_HASH
  // Ignore messages with less than minimum on or off pulses.
  irrecv.setUnknownThreshold(kMinUnknownSize);
#endif  // DECODE_HASH
  irrecv.enableIRIn();  // Start the receiver
}

// The repeating section of the code
void loop() {
  // Check if the IR code has been received.
  if (irrecv.decode(&results)) {
    // Display a crude timestamp.
    uint32_t now = millis();
    Serial.printf(D_STR_TIMESTAMP " : %06u.%03u\n", now / 1000, now % 1000);
    // Check if we got an IR message that was to big for our capture buffer.
    if (results.overflow)
      Serial.printf(D_WARN_BUFFERFULL "\n", kCaptureBufferSize);
    // Display the library version the message was captured with.
    Serial.println(D_STR_LIBRARY "   : v" _IRREMOTEESP8266_VERSION_ "\n");
    // Display the basic output of what we found.
    Serial.print(resultToHumanReadableBasic(&results));
    // Display any extra A/C info if we have it.
    String description = IRAcUtils::resultAcToString(&results);
    if (description.length()) Serial.println(D_STR_MESGDESC ": " + description);
    yield();  // Feed the WDT as the text output can take a while to print.
#if LEGACY_TIMING_INFO
    // Output legacy RAW timing info of the result.
    Serial.println(resultToTimingInfo(&results));
    yield();  // Feed the WDT (again)
#endif  // LEGACY_TIMING_INFO
    // Output the results as source code
    Serial.println(resultToSourceCode(&results));
    Serial.println();    // Blank line between entries
    yield();             // Feed the WDT (again)
  }
}

Reading IR Codes

To use this application, first open the serial monitor. Then point your remote at it and press one of the remote's buttons. Information about the IR signal sent by the remote will be displayed. The number we are interested in is called uint64_t data, like in the following screenshot. Write down the name of the button and the corresponding uint64_t data - that is the info we use for our remote emulator. For example, pressing the on/off button generates 0xA8B47 - your remote will likely be different. The complete code is in a later blog post!

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Patriot Geek

Friday, May 22, 2020

ATOM Matrix: Grove IR Remote Module

IR Remote Module

Application: Grove-IR-Remote-02 (Same as IRrecvDumpV2)

Reading IR Codes

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