12-bit converters aren't supported, but it says they are

[magnusdahlstrand]

MCP3202, MCP3204 and MCP3208 are not supported and are commented out in the code. This is not mentioned in the documentation, and with the name MCP3XXXX (indicating the MCP32XXX variations are included) they should be, or at least the documentation should say that they are not supported and the ADC_UNSUPPORTED_CONFIGURATION value will be returned every time they're used.