Propeller Development Board

    Schematics and source code for the latest design can be downloaded below.

    Creating a prototype of a project often resulted in a rats nest of wires on a breadboard. And almost always you would have the same base items in your design. Most often, a microcontroller of some description, interface circuitry of some sort to program and interface with the microcontroller, perhaps a few led's and even a button or two. This can take up a lot of bread board space and you haven't even begun your project yet. This has always been a bit of a thorn in the side for me and over the years I have tried to make a few attempts at alleviating that problem.

 This was my first attempt. It had a lot of options, some good, some bad. But only a few were really of use.
The features of this design were:
- Vin, +5.0, and +3.3v power.
- SD Card interface(on the underside of the board).
- RS232 interface.
- 2 10K Potentiometers.
- Socketed Op-Amp.
- 8 Tact switches.
- 8 Position DIP switches.
- 16 LED's
- 6 Digit multiplexed 7 segment Displays.

    Most of the options were of no use. The RS232 wasn't even used. Originally, it was to be used to program a Propeller microcontroller. Right from the start I instead used a USB to Serial converter to do the job. Also, the OP-Amp was a bit of a pain to use, and I just ended up putting the IC on the breadboard instead. 16 LED's is overkill, as I typically only ever use a few. Same with 8 tact switches. The SD card I never used at the time, but I tend to use occasionally now. I've never used the dip switches or the 7 segment displays.
    The most used items were the 3 power supply outputs, as well as the EEPROM. The EEPROM as it is essential for the Prop, and well, everything needs power....

    The next development board I designed wasn't for initial prototyping, but for semi-permanent designs.
    This design was compact and efficient. The features on this design are:
- Socketed Prop for easy replacement.
- USB to Serial converter.
- +3.3v regulator.
- 5MHz crystal.
- Reset switch.
- Female pin header for addon boards.

    What was nice about this design, is that the base unit did not contain an EEPROM. This was by design for the reason that the addon board would contain the EEPROM. This way if you swap out addon boards, the program for that addon board will already be present.

Here is the base board from above with an addon board plugged in. This addon board was setup with an AD converter to measure a temp sensor.
If you notice, there is a 3 position DIP switch in the lower right corner. This can set the address of the on board EEPROM. By changing this, it is possible to stack several add on boards to the base unit.
    This was useful for semi permanent projects, but not very useful for intial prototyping since everything is soldered in place.

    This brings me to my latest effort which takes the best of the above and rejects the rest.
    The features of this design are:
- On board Propeller.
- On board +5.0, +3.3v regulators with power LED.
- Reset switch for the Prop.
- USB to Serial converter with TX, RX LED's.
- 4 buffered LED's.
- 4 Active low tact switches.
- 2 10K potentiometers.
- MCP3208 8 channel 10 bit AD converter.
- 2.500v, 4.096v, 0-5v selectable reference for the ADC.
- All 32 pins of the Propeller available.

    So far this design has all the items that I could ask for on board which leaves me the full breadboard space for project design. The PCB was mounted to a piece of lexan using a few left over motherboard mounting standoffs, and the breadboard attached using the included double sided tape. A few rubber feet, and the setup is complete. I am using a 12v wall wart for power which gives me access to +12, +5, and +3.3 for my designs.

    Lastly, I wrote a simple interface .spin file for the Propeller to make interfacing the LED's and AD converter a snap. If you are interested in the design, the schematics as well as the .spin files are available below.

    I hope that this little article was some help and hopefully will inspire you to create your own prototyping platform which will ease your project pain.
Site Admin,
Dec 26, 2013, 4:03 PM
Propeller Prototyping Board
Site Admin,
Dec 26, 2013, 4:02 PM