I have always wanted to access the Rapsberry PI Gpio pins in a safer manner. Those are not 5V tolerant, and need a level shifter.
I came across this really nice level translator chip from TXB0108 from Texas Instruments. It is a bidrectional 3.3 to 5v logic level translator in a really tiny package.
The total pins on the RPI GPIO port that need to be converted are RX+TX, SCL+SDA, (MOSI+MISO+SCK+CS0+CS1) + 8 Pins, totalling 17 pins. With two of those chips, and one Mosfet based logic level translator, I was able to build a board in a small footprint of 22.91mmx37.24 mm.
I got my PCB manufactured from OSH Park, which cost me ~7 USD for three boards. The voltage converter chips I had asked for samples, so I got them for free.
Each set of breakout pins have 5V and GND on corners of that port.
Step 1: PCB arrived, populated and tested
The PCB arrived about 21 days after ordering, and I asked a phone repairman to solder the SMD devices for me. I left the Mosfet unpopulated, because at this moment, I dint have much need for that.
My primary use was to access the UART of the Rpi to control my 3D Printer. The pins on my Gen 7 board are also broken out on the board, and using a direct connection to a UART was the need of the hour for me, because, the MCP2200 chip on the Gen 7 Controller board used to get reset whenever there was an inductive load switched on in the house, like a bell.
The board performed flawlessly, and I no longer have prints stopping midway, when someone rings a bell or turns on a ceiling fan .
If you have like the project, please vote for me using the voting buttons for a contest appearing on the right top corner.
For more detail: Raspberry PI Safe Breakout