Bus Pirate LCD Adapter

February 17, 2012

I was sent a free Bus Pirate LCD adapter v2b PCB from http://dangerousprototypes.com/. I planned to build the PCB with the parts on the schematic however, I found that I couldn’t get the 74HCT595 shift register in quantities less than 25. This chip clocks in 8 bits of serial data on the rising edge of the SCK and moves the clocked data across to the output flip flops on the RCK. It seemed like I could easily find a replacement for this chip.

74HCT595 IEC Logic Symbol

74HCT595 IEC Logic Symbol

I thought that this chip would be easy to replicate with two separate chips. I used a 74HC164 to clock in the serial data and a 74HC273 to clock all 8-bits of data to the output at once. This replicates the original chip.

Bus Pirate Mod Schematic

Bus Pirate Mod Schematic

I built this on a breadboard with DIL packages of the two above chips to test that they were working as expected. They seemed to function as expected.

Breadboard with logic chips

Breadboard with logic chips

I also found that the 16 bit header output wasn’t suitable for the LCD screens I wanted to test. I wanted a 2×8 shrouded header which I could easily plug in many different screens into for testing. I made these two modifications on veroboard and added them to the original PCB. The end result was messy and delicate.

Modified Bus Pirate Adapter

Modified Bus Pirate Adapter

So I decided that I would attempt to redesign the LCD adapter with these two changes. I wanted to keep the 16 pin straight header as well as the 2×8 header so that you could use either when you assembled the board. The board is a 5cm x 5cm size as this was cheap to get produced by Seeed Studio’s Fusion PCB service.

Top Layer

Top Layer

Download Gerbers

Download Eagle Files

Here are some photos of the fully assembled board:

Chips Soldered

Chips Soldered

Fully assembled board (minus jumpers)

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