Chapter 9 - AD Converter

Ada rewrite of the Freenove “AD Converter” lesson for the Raspberry Pi Pico.

The sketch on GP26 (ADC0) prints three representations of the same potentiometer on one UART line:

• RP.ADC.Analog_Value - the 12-bit code (0 .. 4095)
• RP.ADC.Microvolts - that code scaled by the HAL with a Float
• Pico.Analog.Input.Volts - a 32-bit ordinary fixed-point subtype (delta 0.1 mV, 'Small => 2**(-16)), converted from the count by multiply-first / divide-second

The chapter is the notes I needed before that line made sense:

• AGND and ADC_VREF are a filtered analogue pair, not a second isolated supply. ADC3 (VSYS/3) and ADC4 (the on-chip temperature sensor) are not available as general inputs.
• The RP2040 ADC has dead zones at both rails. On my board the floor sits around 19 counts (~15 mV) and the ceiling around 4081. Software clamps those to Volts'First and Volts'Last.
• Free_Running plus a 2 Hz Put_Line leaves stale samples in the FIFO. The sketch uses One_Shot.
• The three columns are three conversions, not three formats of one sample. They may differ by a count or two.
• Sketch_09_1_ADC is No_Return under the Jorvik profile. The handler logs on Ada.Text_IO and re-raises; the embedded runtime then halts. Fine for a sample you reset with BOOTSEL. SPARK would want an outer loop instead.

Built against rp2040_hal / the Pico BSP. Watch the UART with CoolTerm (or any 115200 8N1 terminal).

Read the full tutorial at Chapter 9 - AD Converter: three ways to read a voltage, GNATdoc documentation, SourceForge repository