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.
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.
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.
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.
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.
Here are some photos of the fully assembled board:
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