The i2c Analogue PCB's arrived and the first one has been assembled. For this I decided to add it to the top of a version 1.2 Weather Pi.
The boards will be used on a Raspberry Pi model A so I used a 26 pin extended header to connect the boards to the Pi.
As part of development of Weather Pi, I wanted to test out Analogue sensors with the Raspberry Pi. I had a look a some of the commercial available PCB's such as Custard Pi and Quick2Wire but was shocked at the high price (£15 - £20 plus P&P).
The PCF8591 I2C chips that these units are based on can be purchased for about £1 so that does not justify the high price. This includes postage from China.
Introducing the Analogue Breakout Version 1.2 PCB.
The PCB uses 2 x PCF8591P i2c chips providing 8 ports for analogue sensors. The chips are hard coded on the PCB to use i2c channel 48 and 4c.
The PCB has a jumper to allow the chips to run at 3.3 volts or 5 volts. At the time of designing I was unsure if it was safe to run the chips at 5v when interfacing with the RaspberryPi. Normally the Pi's only like 3.3 volts.
Also on the PCB are 3 x i2c headers running at 3.3v.
The PCB is compatible with all models of Pi except the compute model. Only the 3.3v, 5v, GND, SDA and SCL pins are used. Using a 5cm board it's not possible to include space for all 40 possible GPIO pins, hence why they run to the edge.
The PCB's were ordered from SeedStudio, and cost about £7 for 10.