stm32: Add support for dual-analog-pad "_C" pins on H7 MCUs.

This commit adds support for the dual-analog-pads on STM32H7 parts.  These
pads/pins are called PA0_C/PA1_C/PC2_C/PC3_C in the datasheet.  They each
have an analog switch that can optionally connect them to their normal pin
(eg PA0).  When the switch is open, the normal and _C pin are independent
pins/pads.

The approach taken in this commit to make these _C pins available to Python
is:
- put them in their own, independent row in the stm32h7_af.csv definition
  file, with only the ADC column defined (they are separate machine.Pin
  entities, and doing it this way keeps make-pins.py pretty clean)
- allow a board to reference these pins in the board's pins.csv file by the
  name PA0_C etc (so a board can alias them, for example)
- these pins (when enabled in pins.csv) now become available like any other
  machine.Pin through both machine.Pin.board and machine.Pin.cpu
- BUT these _C pins have a separate pin type which doesn't have any
  methods, because they don't have any functionality
- these _C pins can be used with machine.ADC to construct the appropriate
  ADC object, either by passing the string as machine.ADC("PA0_C") or by
  passing the object as machine.ADC(machine.Pin.cpu.PA0_C)
- if a board defines both the normal and _C pin (eg both PA0 and PA0_C) in
  pins.csv then it must not define the analog switch to be closed (this is
  a sanity check for the build, because it doesn't make sense to close the
  switch and have two separate pins)

Signed-off-by: Damien George <damien@micropython.org>

1 files changed, 10 insertions, 8 deletions

diff --git a/ports/stm32/boards/make-pins.py b/ports/stm32/boards/make-pins.py
index bfa22d7974..8fb442153f 100755
--- a/ports/stm32/boards/make-pins.py
+++ b/ports/stm32/boards/make-pins.py
@@ -59,6 +59,12 @@ class Stm32Pin(boardgen.Pin):
     def __init__(self, cpu_pin_name):
         super().__init__(cpu_pin_name)
 
+        # Pins ending in "_C" correspond to the analog-only pad of a pair
+        # of dual (analog) pads found on H7 MCUs (eg PA0 and PA0_C pair).
+        self._analog_only = cpu_pin_name.endswith("_C")
+        if self._analog_only:
+            cpu_pin_name = cpu_pin_name[:-2]
+
         # P<port><num> (already verified by validate_cpu_pin_name).
         self._port = cpu_pin_name[1]
         self._pin = int(cpu_pin_name[2:])
@@ -129,11 +135,6 @@ class Stm32Pin(boardgen.Pin):
         # be the P for one channel, and the N for a different channel.
         # e.g. "ADC123_INP12/ADC123_INN11".
         for adc_name in adc.split("/"):
-            if adc_name.startswith("C_"):
-                # Currently unsupported, H7 dual-pad. The C_ADC entries should
-                # only be available directly from machine.ADC (not via the pin
-                # object).
-                continue
             m = re.match("ADC([1-5]+)_(IN[NP]?)([0-9]+)$", adc_name)
             if not m:
                 raise boardgen.PinGeneratorError(
@@ -167,8 +168,9 @@ class Stm32Pin(boardgen.Pin):
         )
 
         # PIN(p_port, p_pin, p_af, p_adc_num, p_adc_channel)
-        return "PIN({:s}, {:d}, pin_{:s}_af, {:s}, {:d})".format(
-            self._port, self._pin, self.name(), adc_units_bitfield, self._adc_channel
+        pin_macro = "PIN_ANALOG" if self._analog_only else "PIN"
+        return "{:s}({:s}, {:d}, pin_{:s}_af, {:s}, {:d})".format(
+            pin_macro, self._port, self._pin, self.name(), adc_units_bitfield, self._adc_channel
         )
 
     # This will be called at the start of the output (after the prefix). Use
@@ -210,7 +212,7 @@ class Stm32Pin(boardgen.Pin):
     def validate_cpu_pin_name(cpu_pin_name):
         boardgen.Pin.validate_cpu_pin_name(cpu_pin_name)
 
-        if not re.match("P[A-K][0-9]+$", cpu_pin_name):
+        if not re.match("P[A-K][0-9]+(_C)?$", cpu_pin_name):
             raise boardgen.PinGeneratorError("Invalid cpu pin name '{}'".format(cpu_pin_name))