a driver for IR "blaster" apps. The device drivers are nonblocking. They do not
require `uasyncio` but are compatible with it.
+NOTE: The receiver is intended to be cross-platform. In testing it has proved
+problematic on ESP8266. The cause is
+[this firmware issue](https://github.com/micropython/micropython/issues/5714)
+which should be fixed in due course.
+
# 1. IR communication
IR communication uses a carrier frequency to pulse the IR source. Modulation
A remote using the NEC protocol is [this one](https://www.adafruit.com/products/389).
-Remotes normally transmit an address and a data byte. The address denotes the
-physical device being controlled. The data is associated with the button on the
-remote. Provision exists for differentiating between a button repeatedly
-pressed and one which is held down; the mechanism is protocol dependent.
+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. Hardware Requirements
[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. The tested chip returns a 0 level on carrier detect, but the
-driver design should ensure operation regardless of sense.
+driver design ensures operation regardless of sense.
In my testing a 38KHz demodulator worked with 36KHz and 40KHz remotes, but this
-is obviously not guaranteed or optimal.
+is obviously neither guaranteed nor optimal.
-The pin used to connect the decoder chip to the target is arbitrary but the
-test programs assume pin X3 on the Pyboard, pin 13 on the ESP8266 and pin 23 on
-ESP32.
+The pin used to connect the decoder chip to the target is arbitrary. The test
+program assumes pin X3 on the Pyboard, pin 23 on ESP32 and pin 13 on ESP8266.
+On the WeMos D1 Mini the equivalent pin is D7.
The transmitter requires a Pyboard 1.x (not Lite) or a Pyboard D. Output is via
an IR LED which will normally need a transistor to provide sufficient current.
There are no dependencies.
The demo can be used to characterise IR remotes. It displays the codes returned
-by each button. This can aid in the design of receiver applications. When the
-demo runs, the REPL prompt reappears: this is because it sets up an ISR context
-and returns. Press `ctrl-d` to cancel it. A real application would run code
-after initialising reception so this behaviour would not occur.
+by each button. This can aid in the design of receiver applications. The demo
+prints "running" every 5 seconds and reports any data received from the remote.
## 3.2 Transmitter
value matching your remote improves the timing and reduces the likelihood of
errors when handling repeats: in 20-bit mode SIRC timing when a button is held
down is tight. A worst-case 20-bit block takes 39ms nominal, yet the repeat
- time is 45ms nominal.
+ time is 45ms nominal. On ESP32 20-bit mode did not work well.
The Sony remote tested issues both 12 bit and 15 bit streams.
The callback takes the following args:
In general applications should provide user feedback of correct reception.
Users tend to press the key again if the expected action is absent.
-Data values passed to the callback are normally positive. Negative values
+Data values passed to the callback are zero or positive. Negative values
indicate a repeat code or an error.
`REPEAT` A repeat code was received.
# 4.2 Receiver platforms
The NEC protocol has been tested against Pyboard, ESP8266 and ESP32 targets.
-The Philips protocols - especially RC-6 - have tighter timing constraints. I
-have not yet tested these, but I anticipate problems.
+The Philips protocols - especially RC-6 - have tighter timing constraints.
+Currently the ESP8266 suffers from [this issue](https://github.com/micropython/micropython/issues/5714)
+which prevented testing.
+
+All modes work on the Pyboard. On ESP32 NEC mode works. Sony works for lengths
+of 12 and 15 bits, but 20 bit mode was not reliable owing to the rate at which
+repeats are transmitted. Philips RC-5 worked, with some "bad block" messages.
+Work is ongoing to characterise ESP32 and ESP8266.
# 4.3 Principle of operation
are set by the subclasses. The `.decode` method is provided in the subclass.
CPU times used by `.decode` (not including the user callback) were measured on
-a Pyboard D SF2W at stock frequency. They were NEC 1ms for normal data, 100μs
+a Pyboard D SF2W at stock frequency. They were: NEC 1ms for normal data, 100μs
for a repeat code. Philips codes: RC-5 900μs, RC-6 mode 0 5.5ms.
# 5 Transmitter
The transistor type is not critical.
-These circuits assume circuits as shown. Here the carrier "off" state is 0V,
+The driver assumes circuits as shown. Here the carrier "off" state is 0V,
which is the driver default. If using a circuit where "off" is required to be
3.3V, the constant `_SPACE` in `ir_tx.py` should be changed to 100.
is set in the constructor. The OOK is performed by dynamically changing the
duty ratio using the timer channel's `pulse_width_percent` method: this varies
the pulse width from 0 to a duty ratio passed to the constructor. The NEC
-protocol defaults to 50%, the Philips ones to 30%.
+protocol defaults to 50%, the Sony and Philips ones to 30%.
The duty ratio is changed by the Timer 5 callback `._cb`. This retrieves the
next duration from the array. If it is not `STOP` it toggles the duty cycle
projects / micorpython_ir.git / blobdiff