Here's a problem I've just spent several hours tracking down...
I assembled the avrlirc project on a solderless breadboard using an STK500 and a FT232RL using the breakout board from Sparkfun. The IR module is powered by the STK500 via the PORTD connector and has filter caps (47 uF and .1uF) on its supply pins. I've found that transmitting data via the FT232 will trigger spurious interrupts from the IR module. Here's what I've done to confirm this:
- I don't see this problem if I use the STK500's second UART instead of the FT232.
- I don't see the problem either if I power the IR module via batteries.
- the problem is lessened but still is present if I add a 100 ohm resistor between V_TARGET and the positive supply of the IR module (as suggested by the IR module datasheet)
I see this problem when I transmit at 115K baud as well as 38.4K.
Is there something I can do to achieve more isolation between the FT232 and the rest of the circuit? I'd like to put the FT232, attiny2313 and IR module all on one PCB eventually.
Sparkfun FT232RL breakout: http://www.sparkfun.com/commerce...