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.__init__.py` should be changed to 100.
+3.3V, the class variable `active_high` should be set `False`.
## 1.2 ESP32 Wiring
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.
+
#### NEC class
+Class `NEC`. Example invocation:
+```python
+from ir_tx.nec import NEC
+```
+
This has an additional method `.repeat` (no args). This causes a repeat code to
be transmitted. Should be called every 108ms if a button is held down.
#### Sony classes
+Classes `SONY_12`, `SONY_15` and `SONY_20`. Example invocation:
+```python
+from ir_tx.sony import SONY_15
+```
+
The SIRC protocol supports three sizes, supported by the following classes:
1. 12 bit (7 data, 5 address) `SONY_12`
2. 15 bit (7 data, 8 address) `SONY_15`
#### Philips classes
+Classes `RC5` and `RC6_M0`. Example invocation:
+```python
+from ir_tx.philips import RC5
+```
+
The RC-5 protocol supports a 5 bit address and 6 or 7 bit (RC5X) data. The
driver uses the appropriate mode depending on the `data` value provided.
changes when the button is released. The application should implement this
behaviour, setting the `toggle` arg of `.transmit` to 0 or 1 as required.
+#### Microsoft MCE class
+
+Class `MCE`. Example invocation:
+```python
+from ir_tx.mce import MCE
+# MCE.init_cs = 3
+```
+There is a separate demo for the `MCE` class because of the need to send a
+message on key release. It is run by issuing:
+```python
+from ir_tx.mcetest import test
+```
+Instructions will be displayed at the REPL.
+
+I have been unable to locate a definitive specification: the protocol was
+analysed by a mixture of googling and experiment. Behaviour may change if I
+acquire new information. The protocol is known as OrtekMCE and the remote
+control is sold on eBay as VRC-1100.
+
+The remote was designed for Microsoft Media Center and is used to control Kodi
+on boxes such as the Raspberry Pi. With a suitable PC driver it can emulate a
+PC keyboard and mouse. The mouse emulation uses a different protocol: the class
+does not currently support it. Pressing mouse buttons and pad will cause the
+error function (if provided) to be called.
+
+This supports a 4 bit address, 6 bit data and 2 bit toggle. The latter should
+have a value of 0 for the first message, 1 for repeat messages, and 2 for a
+final message sent on button release.
+
+The remaining four bits are a checksum which the driver creates. The algorithm
+requires an initial 'seed' value which my testing proved to be 4. However the
+only [documentation](http://www.hifi-remote.com/johnsfine/DecodeIR.html#OrtekMCE)
+I could find stated that the value should be 3. I implemented this as a class
+variable `MCE.init_cs=4`. This enables it to be changed if some receivers
+require 3.
+
# 4. Principle of operation
## 4.1 Pyboard
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. The NEC
-protocol defaults to 50%, the Sony and Philips ones to 30%.
+the pulse width from 0 to a 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
constructor converts the 0-100 duty ratio specified by the subclass to the
0-1023 range used by ESP32.
-# 5. References
-
-[General information about IR](https://www.sbprojects.net/knowledge/ir/)
-
-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)
-
-Philips protocols:
-[RC5](https://en.wikipedia.org/wiki/RC-5)
-[RC5](https://www.sbprojects.net/knowledge/ir/rc5.php)
-[RC6](https://www.sbprojects.net/knowledge/ir/rc6.php)
+## 4.3 Duty ratio
-Sony protocol:
-[SIRC](https://www.sbprojects.net/knowledge/ir/sirc.php)
+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.
projects / micorpython_ir.git / blobdiff