The Straddler Makes AVR Breadboarding Truly Plug And Play


It’s not that breadboarding AVR circuits is difficult. But you have to admit that it takes some time to set everything up. We don’t label the top of our DIP chips so that you know what each pin does just by looking. Which means that wiring up the programmer involves pulling out the datasheet. [Vinnie] found the solution to this problem which is to make one of these interface PCBs for each AVR chip family. The long pins make it easy to drop over the top of your microcontroller, which is where the name comes from.

His first stab at the idea was just a hunk of home etched PCB which broke out the programming pins into the 6-pin ICSP standard. This second rendition uses the 10-pin standard and adds a few extras into the mix. He included decoupling capacitors which need to be used in every circuit anyway. There’s a crystal along with its load capacitors. This clock source is a snap to enable by burning some fuses. If you choose to use the internal oscillator instead this hardware won’t interfere. The LED is used to get you up and running with blinky firmware as quickly as possible. He plans to add jumper in the next revision which can disconnect this components from the I/O pin. Now you just need to add a 10-pin header to that USB keyboard AVR programmer and you’re in business.

17 thoughts on “The Straddler Makes AVR Breadboarding Truly Plug And Play

  1. Nice idea. I would replace the 10 uF electrolytic with a nice small ceramic one. You can get 10V, 10 uF in 0603 shape, and there’s even more choice in 0805. Another option would be to add the CPU on the board itself, which would be nice for experimenting with small pitch SMT stuff on a breadboard.

  2. Clever, haven’t seen it done that way before. The only small downside is that occasionally I use my finger to check the temperature on the MCU, and the Straddler blocks access.

      1. It shouldn’t get hot, or even particularly warm, unless something is wrong. Touching the chip is a primitive but expedient method of making sure it isn’t being stressed by excessive current draw or overvoltage clamping on a pin.

          1. I suppose you could add an analog temperature sensor or thermistor to it, positioned so that the sensor/thermistor physically touches the microprocessor package below it. Then you could wire it so that it makes an LED (red, of course) brighter the hotter it gets (lets more voltage through, for instance). Right?

  3. I created something similar a while back. My main focus was to make it easier to program while breadboarding, and to not have to continually look up the Arduino pin mappings. I didn’t put on the crystal or any of the capacitors in my original design though.

    Now when I whip up a quick prototype using perfboard, I end up just putting headers in for these boards to go in over top of the chip. Rather than doing the extra work of putting the ISP header in the perfboard.

  4. Nice idea, but with a small addition:
    While breadboarding I had some intermittent bugs. After a lot of debugging I found out that the bug always occured at the moment that the pin next to the crystal changed logic state. The capacitive coupling via the breadboard was so big that the crystal, and with it the avr, went crasy.

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