diff --git a/ports/raspberrypi/common-hal/analogio/AnalogFastIn.c b/ports/raspberrypi/common-hal/analogio/AnalogFastIn.c
index 68ca742cdd..bc72e940d1 100644
--- a/ports/raspberrypi/common-hal/analogio/AnalogFastIn.c
+++ b/ports/raspberrypi/common-hal/analogio/AnalogFastIn.c
@@ -39,15 +39,12 @@
 
 #define ADC_FIRST_PIN_NUMBER 26
 #define ADC_PIN_COUNT 4
-// Channel 0 is GPIO26
-#define CAPTURE_CHANNEL 0
-#define CAPTURE_DEPTH 1000
-uint8_t capture_buf[CAPTURE_DEPTH];
 
 void common_hal_analogio_analogfastin_construct(analogio_analogfastin_obj_t *self, const mcu_pin_obj_t *pin, uint8_t *buffer, uint32_t len, uint8_t bytes_per_sample, bool samples_signed, mp_float_t sample_rate) {
 
     // Set pin and channel
     self->pin = pin;
+    claim_pin(pin);
     self->chan = pin->number - ADC_FIRST_PIN_NUMBER;
 
     // Checks on chan value here
@@ -70,6 +67,7 @@ void common_hal_analogio_analogfastin_construct(analogio_analogfastin_obj_t *sel
     adc_init();
     adc_gpio_init(pin->number);
     adc_select_input(self->chan); // chan = pin - 26 ??
+
     // adc_select_input(self->pin->number - ADC_FIRST_PIN_NUMBER);
     adc_fifo_setup(
         true,    // Write each completed conversion to the sample FIFO
@@ -108,6 +106,7 @@ void common_hal_analogio_analogfastin_construct(analogio_analogfastin_obj_t *sel
     // clear any previous activity
     adc_fifo_drain();
     adc_run(false);
+
 }
 
 
diff --git a/ports/raspberrypi/mpconfigport.mk b/ports/raspberrypi/mpconfigport.mk
index 1c4de50c00..1ef4fa45ff 100644
--- a/ports/raspberrypi/mpconfigport.mk
+++ b/ports/raspberrypi/mpconfigport.mk
@@ -26,6 +26,9 @@ CIRCUITPY_NVM = 1
 CIRCUITPY_PULSEIO ?= 1
 CIRCUITPY_WATCHDOG ?= 1
 
+# Use of analogio
+CIRCUITPYTHON_ANALOGFASTIN = 1
+
 # Audio via PWM
 CIRCUITPY_AUDIOIO = 0
 CIRCUITPY_AUDIOBUSIO ?= 1
diff --git a/py/circuitpy_defns.mk b/py/circuitpy_defns.mk
index 7ee6c17588..5c5f05ca3a 100644
--- a/py/circuitpy_defns.mk
+++ b/py/circuitpy_defns.mk
@@ -390,7 +390,9 @@ SRC_COMMON_HAL_ALL = \
 	alarm/time/TimeAlarm.c \
 	alarm/touch/TouchAlarm.c \
 	analogio/AnalogIn.c \
+#ifdef CIRCUITPYTHON_ANALOGFASTIN
 	analogio/AnalogFastIn.c \
+#endif
 	analogio/AnalogOut.c \
 	analogio/__init__.c \
 	audiobusio/I2SOut.c \
diff --git a/shared-bindings/analogio/AnalogFastIn.c b/shared-bindings/analogio/AnalogFastIn.c
index 3eb6ce5d1d..e489fa497e 100644
--- a/shared-bindings/analogio/AnalogFastIn.c
+++ b/shared-bindings/analogio/AnalogFastIn.c
@@ -37,7 +37,37 @@
 #include "shared-bindings/analogio/AnalogFastIn.h"
 #include "shared-bindings/util.h"
 
-// pin, buffer, rate
+
+
+//| class AnalogFastIn:
+//|     """Read analog voltage levels quickly using DMA Capture"""
+//|
+//|     def __init__(self, pin: microcontroller.Pin, buffer: ReadableBuffer, *, sample_rate: int = 500000) -> None:
+//|         """Use the AnalogFastIn on the given pin. Fill the given buffer from ADC read values at the supplied
+///         sample_rate.
+///
+//|         :param ~microcontroller.Pin pin: the pin to read from"""
+//|         :param ~circuitpython_typing.WriteableBuffer buffer: A buffer for samples
+//|         :param int sample_rate: The desired playback sample rate
+///
+//|     Usage::
+///
+//|       import board
+//|       import analogio
+//|       import array
+///
+//|       length = 1000
+//|       mybuffer = array.array("H", [0] * length)
+//|       fadc = analogio.AnalogFastIn(board.GP26, mybuffer)
+//|       fadc.capture()
+//|       fadc.deinit()
+//|       for i in range(length):
+//|           print(i, mybuffer[i])
+///
+///       (Future) The reference voltage varies by platform so use ``reference_voltage`` to read the configured setting.
+///       """
+//|         ...
+///
 STATIC void validate_rate(mp_float_t rate) {
     if (rate < (mp_float_t)1.0f || rate > (mp_float_t)500000.0f) {
         mp_raise_ValueError(translate("sample rate must be 1.0-500000.0 per second"));