Thursday, 6 May 2010

Geeky Advent Rehash.

Well ok, it's five months late but here's is my rushed take on tinkerlog's Geeky Advent widget (instructions here) the interesting quirk with these things being the way an LED is used as a light sensor. I've built it using an ATtiny85 instead of the ATtiny13 which requires a tweak to the code to allow for the slight differences in the ADC registers...

ADC Reference voltage

ADMUX = ( 1 << REFS2 ) | ( 1 << REFS1 ) | ADC2; //internal ref 2.56v, sense on PB4

ADC clock prescaler

ADCSRA = ( 1 << ADEN ) | 7;

prescale set to 7 (divide by 128) as i'm led to 'believe' it improves accuracy if the main chip clock is set to 8Mhz

Fuses set to switch off chip prescaler.
avrdude -c < Your Programmer > -p t85 -U lfuse:w:0xe2:m -U hfuse:w:0xdf:m -U efuse:w:0xff:m

Seems to work ok but may need some tweaking to the 'AMBIENT_LIGHT' variable.
not demonstrated is that the LED's light up one LED, Two LED's, Three LED's, Four LED's on each reset, (apologies for blurry video but i'm using a crap digital camera)

Monday, 3 May 2010

Hacking Car Boot Sales.

What's that?, £3.60 for a thumb joystick!?, i'll not line their pockets says i. So it's off to the great British insitution that is the car boot sale. I managed to pick up two Playstation controllers for the reasonable price of one whole quid (actually the one on the right was a quid, the guy let me have the Sony one for nicks as it had a button missing). Back home and after some deft work with a soldering iron i now have four two axis joysticks (complete with switches), four electric motors , two preset potentiometers AND an LED.That works out about 10p a component, a good days work allround methinks.