diff --git a/src/common/pico_stdlib/include/pico/stdlib.h b/src/common/pico_stdlib/include/pico/stdlib.h
index 7f72376..a35b64f 100644
--- a/src/common/pico_stdlib/include/pico/stdlib.h
+++ b/src/common/pico_stdlib/include/pico/stdlib.h
@@ -56,15 +56,15 @@ extern "C" {
 #include "pico/stdio_semihosting.h"
 #endif
 
-// PICO_CONFIG: PICO_DEFAULT_LED_PIN, Optionally defined a pin that drives a regular LED on the board, default=undefined, group=pico_stdlib
+// PICO_CONFIG: PICO_DEFAULT_LED_PIN, Optionally define a pin that drives a regular LED on the board, group=pico_stdlib
 
-// PICO_CONFIG: PICO_DEFAULT_LED_PIN_INVERTED, 1 if LED is inverted, 0 otherwise, type=int, default=0, group=pico_stdlib
+// PICO_CONFIG: PICO_DEFAULT_LED_PIN_INVERTED, 1 if LED is inverted or 0 if not, type=int, default=0, group=pico_stdlib
 #ifndef PICO_DEFAULT_LED_PIN_INVERTED
 #define PICO_DEFAULT_LED_PIN_INVERTED 0
 #endif
 
-// PICO_CONFIG: PICO_DEFAULT_WS2812_PIN, Optionally defined a pin that controls data to a WS2812 compatible LED on the board, default=undefined, group=pico_stdlib
-// PICO_CONFIG: PICO_DEFAULT_WS2812_POWER_PIN, Optionally defined a pin that controls power to a WS2812 compatible LED on the board, default=undefined, group=pico_stdlib
+// PICO_CONFIG: PICO_DEFAULT_WS2812_PIN, Optionally define a pin that controls data to a WS2812 compatible LED on the board, group=pico_stdlib
+// PICO_CONFIG: PICO_DEFAULT_WS2812_POWER_PIN, Optionally define a pin that controls power to a WS2812 compatible LED on the board, group=pico_stdlib
 
 /*! \brief Set up the default UART and assign it to the default GPIO's
  *  \ingroup pico_stdlib
diff --git a/src/rp2_common/hardware_i2c/include/hardware/i2c.h b/src/rp2_common/hardware_i2c/include/hardware/i2c.h
index 7d6760d..b0886df 100644
--- a/src/rp2_common/hardware_i2c/include/hardware/i2c.h
+++ b/src/rp2_common/hardware_i2c/include/hardware/i2c.h
@@ -48,9 +48,9 @@ extern "C" {
 
 typedef struct i2c_inst i2c_inst_t;
 
-// PICO_CONFIG: PICO_DEFAULT_I2C, Define the default I2C for a board, default=undefined, group=hardware_i2c
-// PICO_CONFIG: PICO_DEFAULT_I2C_SDA_PIN, Define the default I2C SDA, min=0, max=29, default=undefined, group=hardware_i2c
-// PICO_CONFIG: PICO_DEFAULT_I2C_SCL_PIN, Define the default I2C SCL pin, min=0, max=29, default=undefined, group=hardware_i2c
+// PICO_CONFIG: PICO_DEFAULT_I2C, Define the default I2C for a board, group=hardware_i2c
+// PICO_CONFIG: PICO_DEFAULT_I2C_SDA_PIN, Define the default I2C SDA pin, min=0, max=29, group=hardware_i2c
+// PICO_CONFIG: PICO_DEFAULT_I2C_SCL_PIN, Define the default I2C SCL pin, min=0, max=29, group=hardware_i2c
 
 /** The I2C identifiers for use in I2C functions.
  *
diff --git a/src/rp2_common/hardware_spi/include/hardware/spi.h b/src/rp2_common/hardware_spi/include/hardware/spi.h
index a913e67..98fb4bd 100644
--- a/src/rp2_common/hardware_spi/include/hardware/spi.h
+++ b/src/rp2_common/hardware_spi/include/hardware/spi.h
@@ -35,11 +35,11 @@ extern "C" {
  * Each controller can be connected to a number of GPIO pins, see the datasheet GPIO function selection table for more information.
  */
 
-// PICO_CONFIG: PICO_DEFAULT_SPI, Define the default SPI for a board, default=undefined, group=hardware_spi
-// PICO_CONFIG: PICO_DEFAULT_SPI_SCK_PIN, Define the default SPI SCK pin, min=0, max=29, default=undefined, group=hardware_spi
-// PICO_CONFIG: PICO_DEFAULT_SPI_TX_PIN, Define the default SPI TX pin, min=0, max=29, default=undefined, group=hardware_spi
-// PICO_CONFIG: PICO_DEFAULT_SPI_RX_PIN, Define the default SPI RX pin, min=0, max=29, default=undefined, group=hardware_spi
-// PICO_CONFIG: PICO_DEFAULT_SPI_CSN_PIN, Define the default SPI CSN pin, min=0, max=29, default=undefined, group=hardware_spi
+// PICO_CONFIG: PICO_DEFAULT_SPI, Define the default SPI for a board, group=hardware_spi
+// PICO_CONFIG: PICO_DEFAULT_SPI_SCK_PIN, Define the default SPI SCK pin, min=0, max=29, group=hardware_spi
+// PICO_CONFIG: PICO_DEFAULT_SPI_TX_PIN, Define the default SPI TX pin, min=0, max=29, group=hardware_spi
+// PICO_CONFIG: PICO_DEFAULT_SPI_RX_PIN, Define the default SPI RX pin, min=0, max=29, group=hardware_spi
+// PICO_CONFIG: PICO_DEFAULT_SPI_CSN_PIN, Define the default SPI CSN pin, min=0, max=29, group=hardware_spi
 
 /**
  * Opaque type representing an SPI instance.
diff --git a/src/rp2_common/hardware_uart/include/hardware/uart.h b/src/rp2_common/hardware_uart/include/hardware/uart.h
index 69ade78..7cfa78e 100644
--- a/src/rp2_common/hardware_uart/include/hardware/uart.h
+++ b/src/rp2_common/hardware_uart/include/hardware/uart.h
@@ -29,9 +29,9 @@ extern "C" {
 #define PICO_UART_DEFAULT_CRLF 0
 #endif
 
-// PICO_CONFIG: PICO_DEFAULT_UART, Define the default UART used for printf etc, default=undefined, group=hardware_uart
-// PICO_CONFIG: PICO_DEFAULT_UART_TX_PIN, Define the default UART TX pin, min=0, max=29, default=undefined, group=hardware_uart
-// PICO_CONFIG: PICO_DEFAULT_UART_RX_PIN, Define the default UART RX pin, min=0, max=29, default=undefined, group=hardware_uart
+// PICO_CONFIG: PICO_DEFAULT_UART, Define the default UART used for printf etc, group=hardware_uart
+// PICO_CONFIG: PICO_DEFAULT_UART_TX_PIN, Define the default UART TX pin, min=0, max=29, group=hardware_uart
+// PICO_CONFIG: PICO_DEFAULT_UART_RX_PIN, Define the default UART RX pin, min=0, max=29, group=hardware_uart
 
 // PICO_CONFIG: PICO_DEFAULT_UART_BAUD_RATE, Define the default UART baudrate, max=921600, default=115200, group=hardware_uart
 #ifndef PICO_DEFAULT_UART_BAUD_RATE
diff --git a/src/rp2_common/pico_stdio_usb/include/pico/stdio_usb.h b/src/rp2_common/pico_stdio_usb/include/pico/stdio_usb.h
index acb9dce..b85b83b 100644
--- a/src/rp2_common/pico_stdio_usb/include/pico/stdio_usb.h
+++ b/src/rp2_common/pico_stdio_usb/include/pico/stdio_usb.h
@@ -49,7 +49,7 @@
 #define PICO_STDIO_USB_ENABLE_RESET_VIA_BAUD_RATE 1
 #endif
 
-// PICO_CONFIG: PICO_STDIO_USB_RESET_MAGIC_BAUD_RATE, baud rate that if selected causes a reset into BOOTSEL mode (if PICO_STDIO_USB_ENABLE_RESET_VIA_BAUD_RATE==1), default=1200, group=pico_stdio_usb
+// PICO_CONFIG: PICO_STDIO_USB_RESET_MAGIC_BAUD_RATE, baud rate that if selected causes a reset into BOOTSEL mode (if PICO_STDIO_USB_ENABLE_RESET_VIA_BAUD_RATE is set), default=1200, group=pico_stdio_usb
 #ifndef PICO_STDIO_USB_RESET_MAGIC_BAUD_RATE
 #define PICO_STDIO_USB_RESET_MAGIC_BAUD_RATE 1200
 #endif
diff --git a/tools/extract_configs.py b/tools/extract_configs.py
index 3c0a2e7..0c8a881 100755
--- a/tools/extract_configs.py
+++ b/tools/extract_configs.py
@@ -149,7 +149,7 @@ for dirpath, dirnames, filenames in os.walk(scandir):
                                 k, v = (i.strip() for i in item.split('='))
                             except ValueError:
                                 raise Exception('{} at {}:{} has malformed value {}'.format(config_name, file_path, linenum, item))
-                            config_attrs[k] = v.replace('\0', ',') if v != 'undefined' else None
+                            config_attrs[k] = v.replace('\0', ',')
                             all_attrs.add(k)
                             prev = item
                         #print(file_path, config_name, config_attrs)
@@ -178,9 +178,14 @@ for dirpath, dirnames, filenames in os.walk(scandir):
                             all_defines[name][value] = (file_path, linenum)
 
 # Check for defines with missing PICO_CONFIG entries
+resolved_defines = dict()
 for d in all_defines:
     if d not in all_configs and d.startswith("PICO_"):
         logger.warning("Potential unmarked PICO define {}".format(d))
+    # resolve "nested defines" - this allows e.g. USB_DPRAM_MAX to resolve to USB_DPRAM_SIZE which is set to 4096 (which then matches the relevant PICO_CONFIG entry)
+    for val in all_defines[d]:
+        if val in all_defines:
+            resolved_defines[d] = all_defines[val]
 
 for config_name in all_configs:
 
@@ -189,8 +194,8 @@ for config_name in all_configs:
     # Check that default values match up
     if 'default' in all_configs[config_name]['attrs']:
         if config_name in all_defines:
-            if all_configs[config_name]['attrs']['default'] not in all_defines[config_name] and (all_configs[config_name]['attrs'].get('type', 'int') != 'bool'):
-                if config_name in ['USB_DPRAM_MAX'] or '/' in all_configs[config_name]['attrs']['default']:
+            if all_configs[config_name]['attrs']['default'] not in all_defines[config_name] and (config_name not in resolved_defines or all_configs[config_name]['attrs']['default'] not in resolved_defines[config_name]):
+                if '/' in all_configs[config_name]['attrs']['default'] or ' ' in all_configs[config_name]['attrs']['default']:
                     continue
                 # There _may_ be multiple matching defines, but arbitrarily display just one in the error message
                 first_define_value = list(all_defines[config_name].keys())[0]