Blinking LEDs and Spinning Servos with Elixir

The post follows the author’s effort to build an automated cat feeder with Elixir on a Raspberry Pi. She begins with a simple LED blink as the first embedded project, then moves on to a servo driven by an Adafruit HAT, and finally adds a VCNL4010 proximity sensor. The main thread is that each step required more wiring, more reading, and more help from library documentation and datasheets.

Reading notes

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• She wanted a feeder that dispenses a very small amount only when the cat is present.
• She chose Elixir for the project and bought a Raspberry Pi starter kit plus a Servo HAT.
• Blinking an LED was the first hardware test after a long break from embedded work.
• The LED example used the elixir_ale library and GPIO pin access through sysfs.
• For the servo, she had to solder the HAT headers and learn from the PCA9685 datasheet.
• She says the Adafruit Python example was hard to reverse engineer, but the datasheet made the task easier.
• The proximity sensor was wired to the Raspberry Pi so the LED could respond to nearby objects.
• She notes that SDA and SCL are the pins that place a device on the i2c bus.
• The next step was to attach the servo and proximity sensor at the same time so the servo could spin when something is near.