Questions and answers gathered from the mailing list. For more details, refer to the mailing list archives. Please tell us which questions are missing :)

Choosing parts

  1. Can I use another IR sensor?

    Yes, there are many models that can work. Check the data sheet and make sure it can use 5V supply voltage. Check the output voltage range and make sure the voltage applied to the MCU input stays below 3.6V, by choosing an appropriate resistor R1. Make sure the modulation bandwidth frequency corresponds to your remote control (practically all use 36 or 38 kHz).

  2. What is a 2k2 or a 27R resistor?

    This is a short form often used in electronics. 2k2 = 2.2 kOhm and 27R = 27 Ohm etc.

  3. Which MAX232 model can I use for the prommer?

    There are basically two generations of this chip, the original MAX232 which according to its data sheet requires 1 uF capacitors, and the MAX232A which requires only 0.1 uF capacitors. That said, the prommer seems to work well with both models. An example part number is MAX232ACPE (the CPE relates to the 16-pin DIL packaging and environmental compatibility).

  4. What about using another type of MCU?

    There is a similar project using an Atmel ATtiny called usbtiny which also can be used with LIRC. Another project called USB Infrared Toy uses a PIC microcontroller.


  1. Can I use a USB-serial adapter?

    Yes, but some might work better than others. I have successfully used an Aten UC-232A adapter (based on the Prolific PL2303 chip). An FTDI-based adapter is also reported to work fine. Both have been used with the bl08 prommer software.

  2. Do I need an external power supply?

    You can use the 5V provided from a USB port. If you also connect the D+ and D- wires to the MCU (through 27 Ohm resistors to be on the safe side), you can verify that the USB communication part of the programmed MCU is working without taking it out of the prommer socket, which is a nice feature.


  1. It doesn't work. Help!

    In 90% of the cases, you have a mistake on the circuit board, for instance a short circuit. Please go over it carefully with visual inspection, then use a multimeter to verify there is no shorts. First leave the MCU out and verify that you have the right supply voltages. Then insert the MCU and verify all voltages again.

  2. Any good pointers to more help and useful information?

    For an excellent introduction to building MC68HC908 hardware and programming it, see Kustaa Nyholm's Fun with HC08 web page, especially the Troubleshooting section.