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Prototyping IC layout hint

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Just a general hint about abstracting chip layout. Currently working on a hd44780 setup with i2c, using a TI PCF8574A. Placed the chip on the breadboard, and wired it all up, and realized how dumb I was. The PCF8574, and most i2c or spi or shift port expanders look like they place all gpio on one half of the chip, and the control pins on the other half. It's easier to wire (no overlapping wires), and neater since it uses less wire, to face the chip with the port pins towards the LCD. This also minimizes bridging over from one side of the breadboard to the other, and leaves more of the breadboard open for plugging things in.


pcf8574a DIP
<- Control Side || Device Side ->
A0  A1  A2  GP0 GP1 GP2 GP3 Gnd
<- Control Side || Device Side ->


The Soic version is nicer. All control pins (Except ground) are on the the left side, and all Port pins are on the right side (Except GP0).


In general, try to look at the chip in sets of pins, instead of individually, for ease in layout.

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