Firmware for the BTLE IR multi-remote project
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readme.md

Bluetooth LE Multi-remote project readme

This is the firmware source code for the Bluetooth LE enabled multi-remote controller project. Read more about the project (including schematics and board layouts) here: http://atomslagstyrken.dk/arduino/tag/remotecontrol/.

Compilation

If you are using a Mac with Xcode you can open the .xcodeproj file and select either "build", "flash" or "fuse" from the targets dropdown and then choose Product -> Build.

As the names indicate, "build" will just compile the project (handy for verifying the syntax), "flash" will compile and flash to the device and "fuse" will set the devices fuses as specified in the Makefile.

If you are not using a Mac with Xcode, just use the normal AVR Libc build commands: make flash or make fuse.

Configuration

Edit the Makefile to specify programmer and port. I am using an AVRISP mkII on the USB port.

Disclaimer

Use at your own risk. Misuse of the code may cause geopolitical instability in susceptible regions. And the code is most likely not complete yet...

Implementation notes

IR code format

Since I have already written some functions for sending RC-5 IR codes, I might as well support those.

But I probably not make a parser that can convert raw data with timing information into an RC-5 code. Instead, I'll just use raw on/off timing pairs. I use one 16 bit unsigned integer for each time code with 5 µs resolution which gives me a range from 0.005 ms to 328 ms in .005 ms intervals. That should be good enough – but time will tell :)

Storage

IR codes will have differing lengths. And the correct way of storing those in the EEPROM would involve some kind of allocation table and stuff. But instead of messing around with all that I've decided to go for a super-simple solution there every IR code uses a fixed size (128 or 256 bytes – something that is a whole multiple of the EEPROM chip's page size). That way I can easily access the code for a specific index.

The data will be in raw time-on, time-off format and terminated by a 0 value (since a 0 ms pulse will never occur).

Thus, for my LG television which uses the NEC1 protocol, an "off" command (address 0x04, command 0xC5) can be stored like this:

90, 45,
6, 6, 6, 6, 6, 17, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
6, 17, 6, 17, 6, 6, 6, 17, 6, 17, 6, 17, 6, 17, 6, 17,
6, 17, 6, 6, 6, 17, 6, 6, 6, 6, 6, 6, 6, 17, 6, 17,
6, 6, 6, 17, 6, 6, 6, 17, 6, 17, 6, 17, 6, 6, 6, 6, 0

UPDATE: These values are from when I stored the values with .1 ms resolution – I now use .005 ms so the actual values are 20 times higher now. For a total of 67 bytes for a code that basically consists of two (!) bytes. Way inefficient! I know.

Recording IR codes

The algorithm for recording IR signals is based on this tutorial from Ladyada.
I use Timer0 on a 200 kHz frequency to keep count of 0.005 ms (5 µs) intervals ("ticks" or "sample periods"). If I get more than 5000 ticks, more than 25 ms has passed and we have exceeded the longest time interval we can store in one byte (almost at least – the real max is 25.5). UPDATE: I still use a maximum time of 25 ms even though I now use 16 bit integers to store pulse widths. When waiting for the first transition to LOW (meaning a 38 kHz signal has been detected) I allow up to 400 25 ms overflows to occur (for a time of 10 seconds). If nothing happens the MCU stops the recording and returns with a timeout error code. Sequences are stored as an array of 16 bit integers which is terminated by a zero value. The recorded values are stored in the array and a pointer is increased for every pulse. The first value if ON time, then OFF time and so on. If an overflow occurs while waiting for a pin LOW state I interpret that as a "signal ended" event (even though it might just be a long no-pulse interval) and overwrite the last pin HIGH data with 0x00 and stop the recording.