Transmitter: ESP32 uses RMT to generate carrier. Test program updated for uasyncio V3

[micorpython_ir.git] / TRANSMITTER.md

diff --git a/TRANSMITTER.md b/TRANSMITTER.md
index 3e3290e28d56f2c66ca8e73d9e33891ae17ed21f..7a70ccae6fc687121b30496f3179ceb27e5defef 100644 (file)
--- a/TRANSMITTER.md
+++ b/TRANSMITTER.md
@@ -13,8 +13,8 @@ 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)`.
 
 ## 1.1 Pyboard Wiring
 
@@ -30,20 +30,16 @@ 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)
-
-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)
+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.
 
 # 2. Dependencies and installation
 
@@ -51,11 +47,17 @@ 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
 
@@ -96,8 +98,7 @@ Basic usage on ESP32:
 ```python
 from machine import Pin
 from ir_tx.nec import NEC
-pins = (Pin(23, Pin.OUT, value = 0), Pin(21, Pin.OUT, value = 0))
-nec = NEC(pins)
+nec = NEC(Pin(23, Pin.OUT, value = 0))
 nec.transmit(1, 2)  # address == 1, data == 2
 ```
 
@@ -269,13 +270,9 @@ 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 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 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 `.trigger` method calls `RMT.write_pulses` and returns with `RMT` operating
 in the background.