README.md

   1 # Device drivers for IR (infra red) remote controls
   2
   3 This repo provides a driver to receive from IR (infra red) remote controls and
   4 a driver for IR "blaster" apps. The device drivers are nonblocking. They do not
   5 require `uasyncio` but are compatible with it, and are designed for standard
   6 firmware builds.
   7
   8 The receiver is cross platform and has been tested on Pyboard, ESP8266, ESP32
   9 and Raspberry Pi Pico.
  10
  11 In a typical use case the receiver is employed at the REPL to sniff the address
  12 and data values associated with buttons on a remote control. The transmitter is
  13 then used in an application to send those codes, emulating the remote control.
  14
  15 Other use cases involve running the receiver in an application. This enables an
  16 IR remote to control a device such as a robot.
  17
  18 #### [Receiver docs](./RECEIVER.md)
  19
  20 The transmitter driver is compatible with Pyboard (1.x and D series) and ESP32.
  21 ESP8266 is unsupported; it seems incapable of generating the required signals.
  22
  23 #### [Transmitter docs](./TRANSMITTER.md)
  24
  25 # 1. IR communication
  26
  27 IR communication uses a carrier frequency to pulse the IR source. Modulation
  28 takes the form of OOK (on-off keying). There are multiple protocols and at
  29 least three options for carrier frequency: 36, 38 and 40KHz.
  30
  31 In the case of the transmitter the carrier frequency is a runtime parameter:
  32 any value may be specified. The receiver uses a hardware demodulator which
  33 should be purchased for the correct frequency. The receiver device driver sees
  34 the demodulated signal and is hence carrier frequency agnostic.
  35
  36 Remotes transmit an address and a data byte, plus in some cases an extra value.
  37 The address denotes the physical device being controlled. The data defines the
  38 button on the remote. Provision usually exists for differentiating between a
  39 button repeatedly pressed and one which is held down; the mechanism is protocol
  40 dependent.
  41
  42 # 2. Supported protocols
  43
  44 The drivers support NEC and Sony protocols plus two Philips protocols, namely
  45 RC-5 and RC-6 mode 0. There is also support for the OrtekMCE protocol used on
  46 VRC-1100 remotes. These originally supported Microsoft Media Center but can be
  47 used to control Kodi and (with a suitable receiver) to emulate a PC keyboard.
  48
  49 Examining waveforms from various remote controls it is evident that numerous
  50 protocols exist. Some are doubtless proprietary and undocumented. The supported
  51 protocols are those for which I managed to locate documentation. My preference
  52 is for the NEC version. It has conservative timing and good provision for error
  53 detection. RC-5 has limited error detection, and RC-6 mode 0 has rather fast
  54 timing.
  55
  56 A remote using the NEC protocol is [this one](https://www.adafruit.com/products/389).
  57
  58 # 3. Hardware Requirements
  59
  60 These are discussed in detail in the relevant docs; the following provides an
  61 overview.
  62
  63 The receiver is cross-platform. It requires an IR receiver chip to demodulate
  64 the carrier. The chip must be selected for the frequency in use by the remote.
  65 For 38KHz devices a receiver chip such as the Vishay TSOP4838 or the
  66 [adafruit one](https://www.adafruit.com/products/157) is required. This
  67 demodulates the 38KHz IR pulses and passes the demodulated pulse train to the
  68 microcontroller.
  69
  70 In my testing a 38KHz demodulator worked with 36KHz and 40KHz remotes, but this
  71 is obviously neither guaranteed nor optimal.
  72
  73 The transmitter requires a Pyboard 1.x (not Lite), a Pyboard D or an ESP32.
  74 Output is via an IR LED which will need a transistor to provide sufficient
  75 current. The ESP32 requires an extra transistor to work as a transmitter.
  76
  77 ## 3.1 Carrier frequencies
  78
  79 These are as follows. The Samsung and Panasonic remotes appear to use
  80 proprietary protocols and are not supported by these drivers.
  81
  82 | Protocol  | F KHz | How found     | Support |
  83 |:---------:|:-----:|:-------------:|:-------:|
  84 | NEC       | 38    | Measured      | Y       |
  85 | RC-5 RC-6 | 36    | Spec/measured | Y       |
  86 | Sony      | 40    | Spec/measured | Y       |
  87 | MCE       | 38    | Measured      | Y       |
  88 | Samsung   | 38    | Measured      | N       |
  89 | Panasonic | 36.3  | Measured      | N       |
  90
  91 # 4. References
  92
  93 Sources of information about IR protocols. The `sbprojects.net` site is an
  94 excellent resource.
  95 [General information about IR](https://www.sbprojects.net/knowledge/ir/)
  96
  97 The NEC protocol:
  98 [altium](http://techdocs.altium.com/display/FPGA/NEC+Infrared+Transmission+Protocol)
  99 [circuitvalley](http://www.circuitvalley.com/2013/09/nec-protocol-ir-infrared-remote-control.html)
 100 [sbprojects.net](https://www.sbprojects.net/knowledge/ir/nec.php)
 101
 102 Philips protocols:
 103 [RC5 Wikipedia](https://en.wikipedia.org/wiki/RC-5)
 104 [RC5 sbprojects.net](https://www.sbprojects.net/knowledge/ir/rc5.php)
 105 [RC6 sbprojects.net](https://www.sbprojects.net/knowledge/ir/rc6.php)
 106
 107 Sony protocol:
 108 [SIRC sbprojects.net](https://www.sbprojects.net/knowledge/ir/sirc.php)
 109
 110 MCE protocol:
 111 [OrtekMCE](http://www.hifi-remote.com/johnsfine/DecodeIR.html#OrtekMCE)
 112
 113 IR decoders (C sourcecode):
 114 [in the Linux kernel](https://github.com/torvalds/linux/tree/master/drivers/media/rc)