garthoff / pilight_firmware

Prefilter for 433 MHz remotes (and similar protocolls) written for an attiny45

pilight firmware

this is an rf receiver prefilter for pilight build with an ATTiny45 / 85. it prefilters the received signal to reduce the load for pilight (http://www.pilight.org). you be warned: this could potentionally damage your raspberry pi and also other hardware. i take no responsability for any damages! use at your own risk!

1. Install avrgcc:

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sudo apt-get install gcc-avr avr-libc

2. Install modified avrdude:

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wget http://project-downloads.drogon.net/files/avrdude_5.10-4_armhf.deb
wget http://project-downloads.drogon.net/files/avrdude-doc_5.10-4_all.deb
sudo dpkg -i avrdude_5.10-4_armhf.deb
sudo dpkg -i avrdude-doc_5.10-4_all.deb

3. Calculate the MIN_PULSELENGTH and MAX_PULSELENGTH values

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MIN_PULSELENGTH =  ( shortest expected pulse - 10% ) / 10
MAX_PULSELENGTH =  ( longest expected pulse + 10% ) / 10

the shortest expected pulse is the minimal base pulse-width of all your protocols
the longest expected pulse is the maximal base pulse-width of all your protocols multiplied by 34

4. Compile and program ATTiny:

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make all

Additional info:

###Calculate fuses: http://www.engbedded.com/fusecalc/

###Pinout:

I use this circuit without resistors. if you want you can even power the ATTiny with 3.3V, it works for 4 out 5 ATTiny's, but i think the timing is less accurate.

Name	Raspberry Pi V2	ATTiny45	433 Receiver
MOSI	19	5	-
MISO	21	6	-
SCK	23	7	-
RESET	24	1	-
PI_IN	see pilight cfg	2	-
REC_OUT	-	3	DATA_OUT

to change the pins create an .avrduderc file in your home directory containing (the numbering is wiringpi numbering!):

programmer
	id    = "gpio";
	desc  = "Use sysfs interface to bitbang GPIO lines";
	type  = gpio;
	reset = 8;
	sck   = 11;
	mosi  = 10;
	miso  = 9;
;

###ATTiny85

If you want to program an ATTiny85 add a parameter when calling make:

Make all type=t85