X-Git-Url: https://vault307.fbx.one/gitweb/micorpython_ir.git/blobdiff_plain/a5c58e92f187b72111774f417d82238ec7e3b6eb..1a533f01992659b56d0fa0d52422b1b796897516:/TRANSMITTER.md?ds=inline diff --git a/TRANSMITTER.md b/TRANSMITTER.md index 4f15c65..2093db7 100644 --- a/TRANSMITTER.md +++ b/TRANSMITTER.md @@ -13,8 +13,14 @@ On the Pyboard the transmitter test script assumes pin X1 for IR output. It can be changed, but it must support Timer 2 channel 1. Pins for pushbutton inputs are arbitrary: X3 and X4 are used. The driver uses timers 2 and 5. -On ESP32 the demo uses pins 21 and 23 for IR output and pins 18 and 19 for -pushbuttons. These pins may be changed. +On ESP32 the demo uses pin 23 for IR output and pins 18 and 19 for pushbuttons. +These pins may be changed. The only device resource used is `RMT(0)`. + +On Raspberry Pi Pico the demo uses pin 17 for IR output and pins 18 and 19 for +pushbuttons. These pins may be changed. The driver uses the PIO to emulate a +device similar to the ESP32 RMT. The device driver is +[documented here](./RP2_RMT.md); this is for experimenters and those wanting to +use the library in conjunction with their own PIO assembler code. ## 1.1 Pyboard Wiring @@ -30,20 +36,22 @@ increase power. The transistor type is not critical. 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 class variable `active_high` should be set `False`. +which is the driver default. If using an alternative circuit where "off" is +required to be 3.3V, the class variable `active_high` should be set `False`. ## 1.2 ESP32 Wiring -The ESP32 RMT device does not currently support the carrier option. A simple -hardware gate is required to turn the IR LED on when both the carrier pin and -the RMT pin are high. A suitable circuit is below; the transistor type is not -critical. -![Image](images/gate.png) +The ESP32 RMT device now supports the carrier option, and this driver has been +updated to use it. The same circuits as above may be used to connect to pin 23 +(or other pin, if the code has been adapted). The `active_high` option is not +available on the ESP32 `RMT` object, so any alternative circuit must illuminate +the LED if the pin state is high. + +## 1.3 RP2 Wiring -This simpler alternative uses MOSFETS, but the device type needs attention. The -chosen type has a low gate-source threshold voltage and low Rdson. -![Image](images/gate_mosfet.png) +There is no `active_high` option so the circuit must illuminate the LED if the +pin state is high, as per the above drivers. Test programs use pin 17, but this +can be reassigned. # 2. Dependencies and installation @@ -51,11 +59,17 @@ chosen type has a low gate-source threshold voltage and low Rdson. The device driver has no dependencies. -On ESP32 a firmware version >= V1.12 is required. The Loboris port is not -supported owing to the need for the RMT device. +On ESP32 a firmware version >= V1.14 is required. The Loboris port is not +supported owing to the need for the RMT device and other issues. -The demo program requires `uasyncio` from the official library and `aswitch.py` -from [this repo](https://github.com/peterhinch/micropython-async). +The demo program uses `uasyncio` primitives from +[this repo](https://github.com/peterhinch/micropython-async). Clone the repo to +a directory on your PC: +```bash +$ git clone https://github.com/peterhinch/micropython-async +``` +move to its `v3` directory, and copy the `primitives` directory with its +contents to the filesystem. ## 2.2 Installation @@ -78,13 +92,36 @@ Instructions will be displayed at the REPL. # 3. The driver -This is specific to Pyboard D, Pyboard 1.x (not Lite) and ESP32. +This is specific to Pyboard D, Pyboard 1.x (not Lite), ESP32 and Raspberry Pi +Pico (RP2 architecture chip). It implements a class for each supported protocol, namely `NEC`, `SONY_12`, `SONY_15`, `SONY_20`, `RC5` and `RC6_M0`. Each class is subclassed from a common abstract base class in `__init__.py`. The application instantiates the appropriate class and calls the `transmit` method to send data. +Basic usage on a Pyboard: +```python +from machine import Pin +from ir_tx.nec import NEC +nec = NEC(Pin('X1')) +nec.transmit(1, 2) # address == 1, data == 2 +``` +Basic usage on ESP32: +```python +from machine import Pin +from ir_tx.nec import NEC +nec = NEC(Pin(23, Pin.OUT, value = 0)) +nec.transmit(1, 2) # address == 1, data == 2 +``` +Basic usage on Pico: +```python +from machine import Pin +from ir_tx.nec import NEC +nec = NEC(Pin(17, Pin.OUT, value = 0)) +nec.transmit(1, 2) # address == 1, data == 2 +``` + #### Common to all classes Constructor args: @@ -97,19 +134,40 @@ Constructor args: 3. `verbose=False` If `True` emits (a lot of) debug output. Method: - 1. `transmit(addr, data, toggle=0)` Integer args. `addr` and `data` are - normally 8-bit values and `toggle` is normally 0 or 1; details are protocol - dependent and are described below. + 1. `transmit(addr, data, toggle=0, validate=False)` Args `addr`, `data` and + `toggle` are positive integers. The maximum vaues are protocol dependent. If + `validate` is `True` passed values are checked and a `ValueError` raised if + they are out of range. If `validate` is false invalid bits are silently + discarded. For example if an address of 0x11 is passed to `MCE.transmit`, the + address sent will be 1 because that protocol supports only a four bit address + field. The `toggle` field is unused by some protocols when 0 should be passed. + +Class method: + 1. `active_low` No args. Pyboard only. A `ValueError` will be thrown on ESP32. + The IR LED drive circuit is usually designed to turn the LED on if the driver + pin is high. If it has opposite polarity the method must be called before + instantiating the class - it will be ineffective if called later. + +Class varaible: + 1. `timeit=False` If `True` the `.transmit` method times itself and prints the + result in μs. The `transmit` method is synchronous with rapid return. Actual transmission -occurs as a background process, on the Pyboard controlled by timers 2 and 5. -Execution times on a Pyboard 1.1 were 3.3ms for NEC, 1.5ms for RC5 and 2ms -for RC6. - -Class variable: - 1. `active_high=True` Normally the IR LED drive circuit turns the LED on if - the pin goes high. If it works with the opposite polarity the variable should - be set `False` before instantiating. +occurs as a background process, on the Pyboard controlled by timers 2 and 5. On +ESP32 the RMT class is used. Execution times were measured on a Pyboard 1.1 and +the ESP32 reference board without SPIRAM. Tests were done at stock frequency and +with `validate=True`, `verbose=False`. A small saving could be achieved by +skipping validation. + +| Protocol | ESP32 | Pyboard | +|:--------:|:-----:|:-------:| +| NEC | 7.8ms | 3.2ms | +| SONY12 | 3.2ms | 1.3ms | +| SONY15 | 3.6ms | 1.5ms | +| SONY20 | 4.5ms | 1.9ms | +| RC5 | 4.9ms | 1.5ms | +| RC6_M0 | 6.0ms | 2.0ms | +| MCE | 6.7ms | 2.0ms | #### NEC class @@ -199,8 +257,6 @@ require 3. # 4. Principle of operation -## 4.1 Pyboard - The classes inherit from the abstract base class `IR`. This has an array `.arr` to contain the duration (in μs) of each carrier on or off period. The `transmit` method calls a `tx` method of the subclass which populates this @@ -212,30 +268,85 @@ this is required for bi-phase (manchester) codings. The `.add` method takes a single μs time value and adds it to the last value in the array: this pulse lengthening is used in bi-phase encodings. -On completion of the subclass `.tx`, `.transmit` appends a special `STOP` value -and initiates physical transmission which occurs in an interrupt context. +On completion of the subclass `.tx`, `.transmit` calls `.trigger` which +initiates transmission as a background process. Its behaviour is platform +dependent. + +## 4.1 Pyboard -This is performed by two hardware timers initiated in the constructor. Timer 2, -channel 1 is used to configure the output pin as a PWM channel. Its frequency -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. +Tramsmission is performed by two hardware timers initiated in the constructor. +Timer 2, channel 1 is used to configure the output pin as a PWM channel. Its +frequency 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 the duty ratio passed to the constructor. 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 -and re-initialises T5 for the new duration. +and re-initialises T5 for the new duration. If it is `STOP` it ensures that the +duty ratio is set to the `_SPACE` + +Here `.trigger` appends a special `STOP` value and initiates physical +transmission by calling the Timer5 callback. ## 4.2 ESP32 -The carrier is output continuously at the specified duty ratio. A pulse train -generated by the RMT instance drives a hardware gate such that the IR LED is -lit only when both carrier and RMT are high. +The RMT class now supports `carrier_freq` and `carrier_duty_percent` +constructor args, so the base class `IR` (in `__init__.py`) uses these to +enable the OOK (on-off keying) waveform. -The carrier is generated by PWM instance `.pwm` running continuously. The ABC -constructor converts the 0-100 duty ratio specified by the subclass to the -0-1023 range used by ESP32. +The `.trigger` method calls `RMT.write_pulses` and returns with `RMT` operating +in the background. ## 4.3 Duty ratio In every case where I could find a specified figure it was 30%. I measured that from a variety of remotes, and in every case it was close to that figure. + +# 5. Unsupported protocols + +You can use the receiver module to capture an IR burst and replay it with the +transmitter. This enables limited support for unknown protocols. This is +strictly for experimenters and I haven't documented it in detail. + +There are two limitations. The first is timing accuracy: both receiving and +transmitting processes introduce some timing uncertainty. This is only likely +to be a practical problem with fast protocols. In brief testing with a known +protocol the scripts below worked. + +The more tricky problem is handling repeat keys: different protocols use widely +varying approaches. If repeat keys are to be supported some experimentation and +coding is likely to be required. + +The following captures a single burst and saves it to a file: +```python +from ir_rx.acquire import test +import ujson + +lst = test() # May report unsupported or unknown protocol +with open('burst.py', 'w') as f: + ujson.dump(lst, f) +``` +This replays it: +```python +from ir_tx import Player +from sys import platform +import ujson + +if platform == 'esp32': + from machine import Pin + pin = (Pin(23, Pin.OUT, value = 0), Pin(21, Pin.OUT, value = 0)) +else: + from pyb import Pin, LED + pin = Pin('X1') +with open('burst.py', 'r') as f: + lst = ujson.load(f) +ir = Player(pin) +ir.play(lst) +``` +The `ir_tx.Player` class is a minimal subclass supporting only the `.play` +method. This takes as an arg an iterable comprising time values of successive +mark and space periods (in μs). + +The `ir_rx.acquire.test` function makes assumptions about the likely maximum +length and maximum duration of a burst. In some cases this may require some +modification e.g. to instantiate `IR_GET` with different args.