I’ve been intending to try driving Switec X25.168 motors using the MCP23008 I²C I/O port expander chip from an Arduino, but it occurs to me that it might be more interesting to try this on a Rasberry Pi. If it works, it will demonstrate a simple and very inexpensive method for driving analog gauges from the Raspberry Pi without the need for high-current drivers.
The MCP23008 provides 8 I/O lines controlled via an I²C interface.
The datasheet is available here. The pins are rated to source and sink 20mA each. That’s around half what an Arduino offers, but should be (just) enough to drive our little Switec steppers. These chips are available from Adafruit, along with the doubly awesome 16-port MCP23017.
MCP23008 – i2c 8 input/output port expander: Add another 8 pins to your microcontroller using a MCP23008 port expander. The MCP23008 uses two i2c pins (these can be shared with other i2c devices), and in exchange gives you 8 general purpose pins. You can set each of 8 pins to be input, output, input with a pullup or open drain. There’s even the ability to get an interrupt via an external pin when any of the inputs change so you don’t have to keep polling the chip. (read more)
MCP23017 – i2c 16 input/output port expander: Add another 16 pins to your microcontroller using a MCP23017 port expander. The MCP23017 uses two i2c pins (these can be shared with other i2c devices), and in exchange gives you 16 general purpose pins. You can set each of 16 pins to be input, output, input with a pullup or open drain. There’s even the ability to get an interrupt via an external pin when any of the inputs change so you don’t have to keep polling the chip. (read more)
Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, TinyGO, or even use the Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for CircuitPython, MakeCode, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.