Add - Expander Pin Definition

[brentru]

This pull request introduces a new "expanders" component type. The expanders being supported by this pull request are GPIO-specific expanders over I2C. However, it aims to be extensible to support multiple types of peripheral expansions over i2c, not just GPIO.

Addresses: adafruit/Wippersnapper_Protobuf#156

---

• Added a new JSON schema components/expanders/schema.json to define the structure and validation rules for expander component definitions.
• Added initial definition files for several expander chips, including:
  • ads7128 (Texas Instruments, 8-channel GPIO/ADC)
  • aw9523 (Awinic, 16-pin GPIO/LED driver)
  • mcp23017 (Microchip, 16-pin GPIO expander)
  • pcf8574 (TI, 8-pin I2C GPIO)
  • pcf8575 (TI, 16-pin I2C GPIO)
  • pi4ioe5v6408 (Diodes Inc., 8-pin GPIO)
  • tca8418 (TI, 18-pin GPIO/keyboard matrix)

[brentru]

NOTE: This API is for v2, in development and should not be merged (I think - Loren can correct me) yet.

[tyeth]

@brentru had a first pass. Minor changes.
We'll also need to distinguish how many neopixels can be on the strand at max (varies with chip and firmware) along with the pins allowed for neopixel (and the fact only ONE pin can be used at a time).

[tyeth]

And I forgot to mention that the documentation urls should all point to https://learn.adafruit.com/adafruit-attiny817-seesaw which covers all the seesaw basic boards.

[brentru]

@tyeth I've made the requested changes. Could you please re-review this PR?

[tyeth]

@brentru had a first pass. Minor changes. We'll also need to distinguish how many neopixels can be on the strand at max (varies with chip and firmware) along with the pins allowed for neopixel (and the fact only ONE pin can be used at a time).

What did you think about this situation? Do we need a flag to distinguish support for the higher clock speed neopixels/dotstars versus basic PWM?

Also, my first review only showed me the 3 attiny component defs, I now see there are ten components that will need verifying so I'll get through them as soon as I can.

[brentru]

Do we need a flag to distinguish support for the higher clock speed neopixels/dotstars versus basic PWM?

Yeah - I think we'll want a flag for each pin's API capability. If it is compatible with the WipperSnapper API, we should have IO present the pin as an option in the component.

[brentru]

@lorennorman @tyeth I have changed the board schema (see this PR) and harmonized it with the component repo.

@tyeth Additionally - I have addressed and resolved your comments from above

[tyeth]

Just one minor blip in find+replace, plus the channels field being name as integer (ok)

[tyeth]

Looks great, thanks Brent (nice update on pattern too)

[brentru]

Pattern matches existing component name patterns now