-# micropython_ir
-Nonblocking device drivers to receive from IR remotes and for IR "blaster" apps.
+# Device drivers for IR (infra red) remote controls
+
+This repo provides a driver to receive from IR (infra red) remote controls and
+a driver for IR "blaster" apps. The device drivers are nonblocking. They do not
+require `uasyncio` but are compatible with it, and are designed for standard
+firmware builds.
+
+The receiver is cross platform and has been tested on Pyboard, ESP8266, ESP32
+and Raspberry Pi Pico.
+
+In a typical use case the receiver is employed at the REPL to sniff the address
+and data values associated with buttons on a remote control. The transmitter is
+then used in an application to send those codes, emulating the remote control.
+
+Other use cases involve running the receiver in an application. This enables an
+IR remote to control a device such as a robot. This may be problematic on some
+platforms. Please see [section 4](./README.md#4-receiver-limitations).
+
+## Raspberry Pi Pico note
+
+Early firmware has [this issue](https://github.com/micropython/micropython/issues/6866)
+affecting USB communication with some PC's. This is now fixed. Please ensure
+you are using up to date firmware.
+
+#### [Receiver docs](./RECEIVER.md)
+
+The transmitter driver is compatible with Pyboard (1.x and D series) and ESP32.
+ESP8266 is unsupported; it seems incapable of generating the required signals.
+
+#### [Transmitter docs](./TRANSMITTER.md)
+
+# 1. IR communication
+
+IR communication uses a carrier frequency to pulse the IR source. Modulation
+takes the form of OOK (on-off keying). There are multiple protocols and at
+least three options for carrier frequency: 36, 38 and 40KHz.
+
+In the case of the transmitter the carrier frequency is a runtime parameter:
+any value may be specified. The receiver uses a hardware demodulator which
+should be purchased for the correct frequency. The receiver device driver sees
+the demodulated signal and is hence carrier frequency agnostic.
+
+Remotes transmit an address and a data byte, plus in some cases an extra value.
+The address denotes the physical device being controlled. The data defines the
+button on the remote. Provision usually exists for differentiating between a
+button repeatedly pressed and one which is held down; the mechanism is protocol
+dependent.
+
+# 2. Supported protocols
+
+The drivers support NEC and Sony protocols plus two Philips protocols, namely
+RC-5 and RC-6 mode 0. There is also support for the OrtekMCE protocol used on
+VRC-1100 remotes. These originally supported Microsoft Media Center but can be
+used to control Kodi and (with a suitable receiver) to emulate a PC keyboard.
+The Samsung protocol (NEC variant) is also supported.
+
+Examining waveforms from various remote controls it is evident that numerous
+protocols exist. Some are doubtless proprietary and undocumented. The supported
+protocols are those for which I managed to locate documentation. My preference
+is for the NEC version. It has conservative timing and good provision for error
+detection. RC-5 has limited error detection, and RC-6 mode 0 has rather fast
+timing.
+
+A remote using the NEC protocol is [this one](https://www.adafruit.com/products/389).
+
+# 3. Hardware Requirements
+
+These are discussed in detail in the relevant docs; the following provides an
+overview.
+
+The receiver is cross-platform. It requires an IR receiver chip to demodulate
+the carrier. The chip must be selected for the frequency in use by the remote.
+For 38KHz devices a receiver chip such as the Vishay TSOP4838 or the
+[adafruit one](https://www.adafruit.com/products/157) is required. This
+demodulates the 38KHz IR pulses and passes the demodulated pulse train to the
+microcontroller.
+
+In my testing a 38KHz demodulator worked with 36KHz and 40KHz remotes, but this
+is obviously neither guaranteed nor optimal.
+
+The transmitter requires a Pyboard 1.x (not Lite), a Pyboard D, an ESP32 or
+Raspberry Pico (RP2). Output is via an IR LED which will need a transistor to
+provide sufficient current.
+
+## 3.1 Carrier frequencies
+
+These are as follows. The Panasonic remote appears to use a proprietary
+protocol and is not supported by these drivers.
+
+| Protocol | F KHz | How found | Support |
+|:---------:|:-----:|:-------------:|:-------:|
+| NEC | 38 | Measured | Y |
+| RC-5 RC-6 | 36 | Spec/measured | Y |
+| Sony | 40 | Spec/measured | Y |
+| MCE | 38 | Measured | Y |
+| Samsung | 38 | Measured | Y |
+| Panasonic | 36.3 | Measured | N |
+
+# 4. Receiver limitations
+
+The receiver uses a pin interrupt and depends on a quick response to a state
+change on the pin. This is guaranteed on platforms which support hard IRQ's
+such as the Pyboard and the RP4 Pico. The ESP32 and ESP8266 only support soft
+IRQ's. This means that, if code such as WiFi communication is running
+concurrently, reliable reception may be problematic.
+
+# 5. References
+
+Sources of information about IR protocols. The `sbprojects.net` site is an
+excellent resource.
+[General information about IR](https://www.sbprojects.net/knowledge/ir/)
+
+Also [IRMP](https://www.mikrocontroller.net/articles/IRMP_-_english)
+
+The NEC protocol:
+[altium](http://techdocs.altium.com/display/FPGA/NEC+Infrared+Transmission+Protocol)
+[circuitvalley](http://www.circuitvalley.com/2013/09/nec-protocol-ir-infrared-remote-control.html)
+[sbprojects.net](https://www.sbprojects.net/knowledge/ir/nec.php)
+
+The Samsung protocol:
+[Rustic Engineering](https://rusticengineering.wordpress.com/2011/02/09/infrared-room-control-with-samsung-ir-protocol/)
+[TechDesign Electronics](https://www.techdesign.be/projects/011/011_waves.htm) Waveforms of various protocols.
+
+
+Philips protocols:
+[RC5 Wikipedia](https://en.wikipedia.org/wiki/RC-5)
+[RC5 sbprojects.net](https://www.sbprojects.net/knowledge/ir/rc5.php)
+[RC6 sbprojects.net](https://www.sbprojects.net/knowledge/ir/rc6.php)
+
+Sony protocol:
+[SIRC sbprojects.net](https://www.sbprojects.net/knowledge/ir/sirc.php)
+
+MCE protocol:
+[OrtekMCE](http://www.hifi-remote.com/johnsfine/DecodeIR.html#OrtekMCE)
+
+IR decoders (C sourcecode):
+[in the Linux kernel](https://github.com/torvalds/linux/tree/master/drivers/media/rc)
projects / micorpython_ir.git / blobdiff