diff --git a/lib/oofatfs/ff.c b/lib/oofatfs/ff.c
index 68c662c7a3..b9b347a7d1 100644
--- a/lib/oofatfs/ff.c
+++ b/lib/oofatfs/ff.c
@@ -5392,7 +5392,9 @@ FRESULT f_mkfs (
     const UINT n_fats = 1;      /* Number of FATs for FAT/FAT32 volume (1 or 2) */
     const UINT n_rootdir = 512; /* Number of root directory entries for FAT volume */
     static const WORD cst[] = {1, 4, 16, 64, 256, 512, 0};  /* Cluster size boundary for FAT volume (4Ks unit) */
+#if FF_MKFS_FAT32
     static const WORD cst32[] = {1, 2, 4, 8, 16, 32, 0};    /* Cluster size boundary for FAT32 volume (128Ks unit) */
+#endif
     BYTE fmt, sys, *buf, *pte, part; void *pdrv;
     WORD ss;    /* Sector size */
     DWORD szb_buf, sz_buf, sz_blk, n_clst, pau, sect, nsect, n;
@@ -5464,7 +5466,7 @@ FRESULT f_mkfs (
             }
         }
         if (au > 128) LEAVE_MKFS(FR_INVALID_PARAMETER); /* Too large au for FAT/FAT32 */
-        if (opt & FM_FAT32) {   /* FAT32 possible? */
+        if (FF_MKFS_FAT32 && (opt & FM_FAT32)) {   /* FAT32 possible? */
             if ((opt & FM_ANY) == FM_FAT32 || !(opt & FM_FAT)) {    /* FAT32 only or no-FAT? */
                 fmt = FS_FAT32; break;
             }
@@ -5641,6 +5643,7 @@ FRESULT f_mkfs (
         do {
             pau = au;
             /* Pre-determine number of clusters and FAT sub-type */
+#if FF_MKFS_FAT32
             if (fmt == FS_FAT32) {  /* FAT32 volume */
                 if (pau == 0) { /* au auto-selection */
                     n = sz_vol / 0x20000;   /* Volume size in unit of 128KS */
@@ -5651,7 +5654,9 @@ FRESULT f_mkfs (
                 sz_rsv = 32;    /* Number of reserved sectors */
                 sz_dir = 0;     /* No static directory */
                 if (n_clst <= MAX_FAT16 || n_clst > MAX_FAT32) LEAVE_MKFS(FR_MKFS_ABORTED);
-            } else {                /* FAT volume */
+            } else
+#endif
+            {                /* FAT volume */
                 if (pau == 0) { /* au auto-selection */
                     n = sz_vol / 0x1000;    /* Volume size in unit of 4KS */
                     for (i = 0, pau = 1; cst[i] && cst[i] <= n; i++, pau <<= 1) ;   /* Get from table */
@@ -5681,12 +5686,14 @@ FRESULT f_mkfs (
             /* Determine number of clusters and final check of validity of the FAT sub-type */
             if (sz_vol < b_data + pau * 16 - b_vol) LEAVE_MKFS(FR_MKFS_ABORTED);    /* Too small volume */
             n_clst = (sz_vol - sz_rsv - sz_fat * n_fats - sz_dir) / pau;
+#if FF_MKFS_FAT32
             if (fmt == FS_FAT32) {
                 if (n_clst <= MAX_FAT16) {  /* Too few clusters for FAT32 */
                     if (au == 0 && (au = pau / 2) != 0) continue;   /* Adjust cluster size and retry */
                     LEAVE_MKFS(FR_MKFS_ABORTED);
                 }
             }
+#endif
             if (fmt == FS_FAT16) {
                 if (n_clst > MAX_FAT16) {   /* Too many clusters for FAT16 */
                     if (au == 0 && (pau * 2) <= 64) {
@@ -5720,7 +5727,11 @@ FRESULT f_mkfs (
         buf[BPB_SecPerClus] = (BYTE)pau;                /* Cluster size [sector] */
         st_word(buf + BPB_RsvdSecCnt, (WORD)sz_rsv);    /* Size of reserved area */
         buf[BPB_NumFATs] = (BYTE)n_fats;                /* Number of FATs */
+#if FF_MKFS_FAT32
         st_word(buf + BPB_RootEntCnt, (WORD)((fmt == FS_FAT32) ? 0 : n_rootdir));   /* Number of root directory entries */
+#else
+        st_word(buf + BPB_RootEntCnt, (WORD) n_rootdir);   /* Number of root directory entries */
+#endif
         if (sz_vol < 0x10000) {
             st_word(buf + BPB_TotSec16, (WORD)sz_vol);  /* Volume size in 16-bit LBA */
         } else {
@@ -5730,6 +5741,7 @@ FRESULT f_mkfs (
         st_word(buf + BPB_SecPerTrk, 63);               /* Number of sectors per track (for int13) */
         st_word(buf + BPB_NumHeads, 255);               /* Number of heads (for int13) */
         st_dword(buf + BPB_HiddSec, b_vol);             /* Volume offset in the physical drive [sector] */
+#if FF_MKFS_FAT32
         if (fmt == FS_FAT32) {
             st_dword(buf + BS_VolID32, GET_FATTIME());  /* VSN */
             st_dword(buf + BPB_FATSz32, sz_fat);        /* FAT size [sector] */
@@ -5739,7 +5751,9 @@ FRESULT f_mkfs (
             buf[BS_DrvNum32] = 0x80;                    /* Drive number (for int13) */
             buf[BS_BootSig32] = 0x29;                   /* Extended boot signature */
             mem_cpy(buf + BS_VolLab32, "NO NAME    " "FAT32   ", 19);   /* Volume label, FAT signature */
-        } else {
+        } else
+#endif
+        {
             st_dword(buf + BS_VolID, GET_FATTIME());    /* VSN */
             st_word(buf + BPB_FATSz16, (WORD)sz_fat);   /* FAT size [sector] */
             buf[BS_DrvNum] = 0x80;                      /* Drive number (for int13) */
@@ -5750,6 +5764,7 @@ FRESULT f_mkfs (
         if (disk_write(pdrv, buf, b_vol, 1) != RES_OK) LEAVE_MKFS(FR_DISK_ERR); /* Write it to the VBR sector */
 
         /* Create FSINFO record if needed */
+#if FF_MKFS_FAT32
         if (fmt == FS_FAT32) {
             disk_write(pdrv, buf, b_vol + 6, 1);        /* Write backup VBR (VBR + 6) */
             mem_set(buf, 0, ss);
@@ -5761,16 +5776,20 @@ FRESULT f_mkfs (
             disk_write(pdrv, buf, b_vol + 7, 1);        /* Write backup FSINFO (VBR + 7) */
             disk_write(pdrv, buf, b_vol + 1, 1);        /* Write original FSINFO (VBR + 1) */
         }
+#endif
 
         /* Initialize FAT area */
         mem_set(buf, 0, (UINT)szb_buf);
         sect = b_fat;       /* FAT start sector */
         for (i = 0; i < n_fats; i++) {          /* Initialize FATs each */
+#if FF_MKFS_FAT32
             if (fmt == FS_FAT32) {
                 st_dword(buf + 0, 0xFFFFFFF8);  /* Entry 0 */
                 st_dword(buf + 4, 0xFFFFFFFF);  /* Entry 1 */
                 st_dword(buf + 8, 0x0FFFFFFF);  /* Entry 2 (root directory) */
-            } else {
+            } else
+#endif
+            {
                 st_dword(buf + 0, (fmt == FS_FAT12) ? 0xFFFFF8 : 0xFFFFFFF8);   /* Entry 0 and 1 */
             }
             nsect = sz_fat;     /* Number of FAT sectors */
@@ -5783,7 +5802,11 @@ FRESULT f_mkfs (
         }
 
         /* Initialize root directory (fill with zero) */
+#if FF_MKFS_FAT32
         nsect = (fmt == FS_FAT32) ? pau : sz_dir;   /* Number of root directory sectors */
+#else
+        nsect = sz_dir;   /* Number of root directory sectors */
+#endif
         do {
             n = (nsect > sz_buf) ? sz_buf : nsect;
             if (disk_write(pdrv, buf, sect, (UINT)n) != RES_OK) LEAVE_MKFS(FR_DISK_ERR);
@@ -5795,7 +5818,7 @@ FRESULT f_mkfs (
     if (FF_FS_EXFAT && fmt == FS_EXFAT) {
         sys = 0x07;         /* HPFS/NTFS/exFAT */
     } else {
-        if (fmt == FS_FAT32) {
+        if (FF_MKFS_FAT32 && fmt == FS_FAT32) {
             sys = 0x0C;     /* FAT32X */
         } else {
             if (sz_vol >= 0x10000) {
diff --git a/lib/oofatfs/ffconf.h b/lib/oofatfs/ffconf.h
index a4a55a0fa2..248987dda3 100644
--- a/lib/oofatfs/ffconf.h
+++ b/lib/oofatfs/ffconf.h
@@ -72,6 +72,12 @@
 #define FF_USE_MKFS     1
 /* This option switches f_mkfs() function. (0:Disable or 1:Enable) */
 
+#ifdef MICROPY_FF_MKFS_FAT32
+#define FF_MKFS_FAT32   MICROPY_FF_MKFS_FAT32
+#else
+#define FF_MKFS_FAT32   0
+#endif
+/* This option switches off FAT32 support in f_mkfs() */
 
 #define FF_USE_FASTSEEK   1
 /* This option switches fast seek function. (0:Disable or 1:Enable) */
diff --git a/ports/atmel-samd/boards/arduino_mkr1300/mpconfigboard.mk b/ports/atmel-samd/boards/arduino_mkr1300/mpconfigboard.mk
index abbdbe87ef..c3d75202bf 100644
--- a/ports/atmel-samd/boards/arduino_mkr1300/mpconfigboard.mk
+++ b/ports/atmel-samd/boards/arduino_mkr1300/mpconfigboard.mk
@@ -9,5 +9,3 @@ CHIP_FAMILY = samd21
 INTERNAL_FLASH_FILESYSTEM = 1
 LONGINT_IMPL = NONE
 CIRCUITPY_FULL_BUILD = 0
-
-CIRCUITPY_RAINBOWIO = 0
diff --git a/ports/atmel-samd/boards/arduino_nano_33_iot/mpconfigboard.mk b/ports/atmel-samd/boards/arduino_nano_33_iot/mpconfigboard.mk
index c940bc02ef..7fe396d698 100644
--- a/ports/atmel-samd/boards/arduino_nano_33_iot/mpconfigboard.mk
+++ b/ports/atmel-samd/boards/arduino_nano_33_iot/mpconfigboard.mk
@@ -11,4 +11,3 @@ LONGINT_IMPL = NONE
 CIRCUITPY_FULL_BUILD = 0
 
 CIRCUITPY_ONEWIREIO = 0
-CIRCUITPY_RAINBOWIO = 0
diff --git a/ports/atmel-samd/boards/arduino_zero/mpconfigboard.mk b/ports/atmel-samd/boards/arduino_zero/mpconfigboard.mk
index 58fd9ca6e4..5ee22c59ad 100644
--- a/ports/atmel-samd/boards/arduino_zero/mpconfigboard.mk
+++ b/ports/atmel-samd/boards/arduino_zero/mpconfigboard.mk
@@ -9,5 +9,3 @@ CHIP_FAMILY = samd21
 INTERNAL_FLASH_FILESYSTEM = 1
 LONGINT_IMPL = NONE
 CIRCUITPY_FULL_BUILD = 0
-
-CIRCUITPY_RAINBOWIO = 0
diff --git a/ports/unix/variants/coverage/mpconfigvariant.h b/ports/unix/variants/coverage/mpconfigvariant.h
index 7902f461bb..2ad0d94bc0 100644
--- a/ports/unix/variants/coverage/mpconfigvariant.h
+++ b/ports/unix/variants/coverage/mpconfigvariant.h
@@ -59,6 +59,7 @@
 #define MICROPY_PY_URE_SUB             (1)
 #define MICROPY_VFS_POSIX              (1)
 #define MICROPY_FATFS_USE_LABEL        (1)
+#define MICROPY_FF_MKFS_FAT32          (1)
 #define MICROPY_PY_FRAMEBUF            (1)
 #define MICROPY_PY_COLLECTIONS_NAMEDTUPLE__ASDICT (1)
 #define MICROPY_PY_COLLECTIONS_ORDEREDDICT (1)
diff --git a/ports/unix/variants/coverage/mpconfigvariant.mk b/ports/unix/variants/coverage/mpconfigvariant.mk
index 69996b2839..563b5ad860 100644
--- a/ports/unix/variants/coverage/mpconfigvariant.mk
+++ b/ports/unix/variants/coverage/mpconfigvariant.mk
@@ -31,18 +31,21 @@ SRC_BITMAP := \
 	$(patsubst ../../%,%,$(wildcard ../../shared-bindings/gifio/*.c ../../shared-module/gifio/*.c)) \
 	shared/runtime/context_manager_helpers.c \
 	displayio_min.c \
+	shared-bindings/bitmaptools/__init__.c \
 	shared-bindings/displayio/Bitmap.c \
+	shared-bindings/rainbowio/__init__.c \
+	shared-bindings/util.c \
+	shared-module/bitmaptools/__init__.c \
 	shared-module/displayio/area.c \
 	shared-module/displayio/Bitmap.c \
 	shared-module/displayio/ColorConverter.c \
-	shared-bindings/bitmaptools/__init__.c \
-	shared-module/bitmaptools/__init__.c \
-	shared-bindings/util.c \
+	shared-module/displayio/ColorConverter.c \
+	shared-module/rainbowio/__init__.c \
 
 $(info $(SRC_BITMAP))
 SRC_C += $(SRC_BITMAP)
 
-CFLAGS += -DCIRCUITPY_GIFIO=1 -DCIRCUITPY_DISPLAYIO_UNIX=1 -DCIRCUITPY_BITMAPTOOLS=1
+CFLAGS += -DCIRCUITPY_GIFIO=1 -DCIRCUITPY_DISPLAYIO_UNIX=1 -DCIRCUITPY_BITMAPTOOLS=1 -DCIRCUITPY_RAINBOWIO=1
 
 SRC_C += coverage.c
 SRC_CXX += coveragecpp.cpp
diff --git a/shared-bindings/rainbowio/__init__.c b/shared-bindings/rainbowio/__init__.c
index 12a33b7d0c..0dfdcd3a45 100644
--- a/shared-bindings/rainbowio/__init__.c
+++ b/shared-bindings/rainbowio/__init__.c
@@ -37,7 +37,8 @@
 //|     ...
 //|
 STATIC mp_obj_t rainbowio_colorwheel(mp_obj_t n) {
-    return MP_OBJ_NEW_SMALL_INT(colorwheel(mp_obj_is_small_int(n) ? MP_OBJ_SMALL_INT_VALUE(n) : mp_obj_get_float(n)));
+    mp_float_t f = mp_obj_get_float(n);
+    return MP_OBJ_NEW_SMALL_INT(colorwheel(f));
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(rainbowio_colorwheel_obj, rainbowio_colorwheel);
 
diff --git a/shared-bindings/rainbowio/__init__.h b/shared-bindings/rainbowio/__init__.h
index 216687518c..3599e3ab3e 100644
--- a/shared-bindings/rainbowio/__init__.h
+++ b/shared-bindings/rainbowio/__init__.h
@@ -27,7 +27,8 @@
 #ifndef CP_SHARED_BINDINGS_RAINBOWIO_INIT_H
 #define CP_SHARED_BINDINGS_RAINBOWIO_INIT_H
 #include <stdint.h>
+#include "py/misc.h"
 
-const int32_t colorwheel(float pos);
+int32_t colorwheel(mp_float_t pos);
 
 #endif // CP_SHARED_BINDINGS_RAINBOWIO_INIT_H
diff --git a/shared-module/rainbowio/__init__.c b/shared-module/rainbowio/__init__.c
index ded0c313f7..a6a2e4974e 100644
--- a/shared-module/rainbowio/__init__.c
+++ b/shared-module/rainbowio/__init__.c
@@ -26,17 +26,21 @@
 
 #include "shared-bindings/rainbowio/__init__.h"
 
-const int32_t colorwheel(float pos) {
-    if (pos > 255) {
-        pos = pos - ((uint32_t)(pos / 256) * 256);
-    }
+int32_t colorwheel(mp_float_t pos) {
+    pos = pos - ((uint32_t)(pos / 256) * 256);
+    int shift1, shift2;
     if (pos < 85) {
-        return (uint8_t)(255 - (pos * 3)) << 16 | (uint8_t)(pos * 3) << 8;
+        shift1 = 8;
+        shift2 = 16;
     } else if (pos < 170) {
         pos -= 85;
-        return (uint8_t)(255 - (pos * 3)) << 8 | (uint8_t)(pos * 3);
+        shift1 = 0;
+        shift2 = 8;
     } else {
         pos -= 170;
-        return (uint8_t)(pos * 3) << 16 | (uint8_t)(255 - (pos * 3));
+        shift1 = 16;
+        shift2 = 0;
     }
+    int p = (int)(pos * 3);
+    return (p << shift1) | ((255 - p) << shift2);
 }
diff --git a/tests/circuitpython/blinky.py b/tests/circuitpython/blinky.py
deleted file mode 100644
index a9412b07c6..0000000000
--- a/tests/circuitpython/blinky.py
+++ /dev/null
@@ -1,2 +0,0 @@
-import digitalio
-import board
diff --git a/tests/circuitpython/rainbows.py b/tests/circuitpython/rainbows.py
new file mode 100644
index 0000000000..664d15de35
--- /dev/null
+++ b/tests/circuitpython/rainbows.py
@@ -0,0 +1,6 @@
+import rainbowio
+
+for i in range(0, 256, 15):
+    print("{:3} {:06x} {:06x}".format(i, rainbowio.colorwheel(i), rainbowio.colorwheel(float(i))))
+for i in range(256, 1024, 128):
+    print("{:3} {:06x}".format(i, rainbowio.colorwheel(i)))
diff --git a/tests/circuitpython/rainbows.py.exp b/tests/circuitpython/rainbows.py.exp
new file mode 100644
index 0000000000..fce94a523a
--- /dev/null
+++ b/tests/circuitpython/rainbows.py.exp
@@ -0,0 +1,24 @@
+  0 ff0000 ff0000
+ 15 d22d00 d22d00
+ 30 a55a00 a55a00
+ 45 788700 788700
+ 60 4bb400 4bb400
+ 75 1ee100 1ee100
+ 90 00f00f 00f00f
+105 00c33c 00c33c
+120 009669 009669
+135 006996 006996
+150 003cc3 003cc3
+165 000ff0 000ff0
+180 1e00e1 1e00e1
+195 4b00b4 4b00b4
+210 780087 780087
+225 a5005a a5005a
+240 d2002d d2002d
+255 ff0000 ff0000
+256 ff0000
+384 007e81
+512 ff0000
+640 007e81
+768 ff0000
+896 007e81
diff --git a/tests/run-tests.py b/tests/run-tests.py
index 4315b5eaaf..b795d6ec94 100755
--- a/tests/run-tests.py
+++ b/tests/run-tests.py
@@ -819,6 +819,7 @@ the last matching regex is used:
         if args.test_dirs is None:
             test_dirs = (
                 "basics",
+                "circuitpython",
                 "micropython",
                 "misc",
                 "extmod",
diff --git a/tests/unix/extra_coverage.py.exp b/tests/unix/extra_coverage.py.exp
index 4be6b20d5d..278c6601a3 100644
--- a/tests/unix/extra_coverage.py.exp
+++ b/tests/unix/extra_coverage.py.exp
@@ -34,11 +34,11 @@ binascii        bitmaptools     btree           cexample
 cmath           collections     cppexample      displayio
 errno           ffi             framebuf        gc
 gifio           hashlib         json            math
-qrio            re              sys             termios
-ubinascii       uctypes         uerrno          uheapq
-uio             ujson           ulab            uos
-urandom         ure             uselect         ustruct
-utime           utimeq          uzlib
+qrio            rainbowio       re              sys
+termios         ubinascii       uctypes         uerrno
+uheapq          uio             ujson           ulab
+uos             urandom         ure             uselect
+ustruct         utime           utimeq          uzlib
 ime
 
 utime           utimeq