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Confessions of a prototyper: #twatch v1/v1b

September 14, 2009 in #twatch, confessions | No comments

twatchv1-image

Last week we released the #twatch v2, an ethernet backpack for 20×4 character LCDs. This wasn’t the only version of the #twatch that we designed. V2 is based on the slick, inexpensive, single-chip ethernet microcontroller, the PIC 18F67J60. The biggest downside to the 18f67J60 is that it can only be programmed an average of 100 times. The limited program cycles make it really difficult to develop the firmware unless you’re a programming genie.

#twatch v1 is a development board for the #twatch firmware. It uses a PIC 24FJ64GA002 microcontoller with a million potential programing cycles, and an ENC28J60 for ethernet access. The design isn’t as advanced as v2, but it’s key to developing the #twatch firmware. We also use the v1 #twatch to diagnose new bugs, like the recent change in Twitter JSON.

You can buy an assembled #twatch v2 PCB for $30, including worldwide shipping. Keep reading for more about the v1 design.

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Confessions of a prototyper: Server v2

August 11, 2009 in confessions | No comments

wsbc2(2)

The original web server on a business card Ian posted at Hack a Day was a homemade single-sided PCB with a few jumper wires. A version 2 was designed on a professional PCB, which opened up a lot of possibilities for new features. We added a 128×128 color Nokia knock-off LCD to make a network-connected photo frame.

The blue wire on the left connects some power pins we forgot to route. The unrouted wire was directly over the connecting wire, which made Eagle Cad’s unrouted indicator invisible. Now we use the zoom-unrouted.ulp script to check for unrouted wires before submitting Gerbers to the board house.

This design remains unpublished because the parts are hard to find. SparkFun stopped carrying the microSD card holder, and a new batch of LCDs didn’t work the same as the old models. The giant DPack 3.3volt regulator (LD117) next to the power jack at the back of the board was also a really expensive, somewhat rare part. We have one extra PCB that we’ll give away on a future free PCB Sunday.

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Confessions of a prototyper: Bus Pirate v1.5

July 31, 2009 in Bus Pirate, Development, confessions | No comments

bp15

The Bus Pirate V2a and V2go weren’t the only design candidates for the Bus Pirate v2 series. Here’s a rendering of the Bus Pirate ‘v1.5′, a design that never saw the light of day. This Bus Pirate was meant to be completely portable. It has an LCD to display the terminal, and a keyboard jack to work with a roll-up rubber keyboard.

Here’s some of the differences between this version and the final v2 series.

  1. This design didn’t include software controlled pull-up resistors. It uses the jumper concept from v1a with SMD resistors.
  2. V1.5 included a Nokia LCD knock off, like the one SparkFun sells for $15. The LCD backlight needs 7volts, so the large SOT223 regulator behind the power supply is a LM317 set to 7volts. The LM317 also supplies the other regulators with 7volts, which is better than the 5V supply to 5volt regulators on the v2a and v2go.
  3. The six hole pattern seen on both sides of the PCB is for the PC keyboard connector. PC keyboards operate at 5volts, so this feature took two of only seven 5volt tolerant pins on the PIC24FJ64.

When we decided to manufacture the Bus Pirate, this design was too complicated and expensive. The code to run the LCD terminal and read the keyboard was big and made it hard to add new protocols. The knock-off Nokia LCDs are really inconsistent too, even different batches from SparkFun require different drivers. We minimized the design first to the v2a, then to the v2go.

In the end, we’re really pleased with the v2go. In retrospect, however, there were a few changes that would have make the whole process smoother. These have been integrated into the updated Bus Pirate v3, which is an even cleaner design that should be easier to manufacture in quantity.

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