diff --git a/libraries/AP_IOMCU/AP_IOMCU.cpp b/libraries/AP_IOMCU/AP_IOMCU.cpp
index cf5b965364..a1ea0a41fa 100644
--- a/libraries/AP_IOMCU/AP_IOMCU.cpp
+++ b/libraries/AP_IOMCU/AP_IOMCU.cpp
@@ -763,12 +763,12 @@ bool AP_IOMCU::check_crc(void)
         hal.console->printf("failed to find %s\n", fw_name);
         return false;
     }
-    uint32_t crc = crc_crc32(0, fw, fw_size);
+    uint32_t crc = crc32_small(0, fw, fw_size);
 
     // pad CRC to max size
 	for (uint32_t i=0; i<flash_size-fw_size; i++) {
 		uint8_t b = 0xff;
-		crc = crc_crc32(crc, &b, 1);
+        crc = crc32_small(crc, &b, 1);
 	}
 
     uint32_t io_crc = 0;
diff --git a/libraries/AP_IOMCU/fw_uploader.cpp b/libraries/AP_IOMCU/fw_uploader.cpp
index b2c14f7b8c..31858b00f1 100644
--- a/libraries/AP_IOMCU/fw_uploader.cpp
+++ b/libraries/AP_IOMCU/fw_uploader.cpp
@@ -397,11 +397,11 @@ bool AP_IOMCU::verify_rev3(uint32_t fw_size_local)
         return ret;
     }
 
-    sum = crc_crc32(0, fw, fw_size_local);
+    sum = crc32_small(0, fw, fw_size_local);
 
     /* fill the rest of CRC with 0xff */
     for (uint32_t i=0; i<fw_size_remote - fw_size_local; i++) {
-        sum = crc_crc32(sum, &fill_blank, 1);
+        sum = crc32_small(sum, &fill_blank, 1);
     }
 
     /* request CRC from IO */
diff --git a/libraries/AP_IOMCU/iofirmware/iofirmware.cpp b/libraries/AP_IOMCU/iofirmware/iofirmware.cpp
index 049ec5905a..50655342a9 100644
--- a/libraries/AP_IOMCU/iofirmware/iofirmware.cpp
+++ b/libraries/AP_IOMCU/iofirmware/iofirmware.cpp
@@ -642,7 +642,7 @@ void AP_IOMCU_FW::calculate_fw_crc(void)
 
     for (unsigned p = 0; p < APP_SIZE_MAX; p += 4) {
         uint32_t bytes = *(uint32_t *)(p + APP_LOAD_ADDRESS);
-        sum = crc_crc32(sum, (const uint8_t *)&bytes, sizeof(bytes));
+        sum = crc32_small(sum, (const uint8_t *)&bytes, sizeof(bytes));
     }
 
     reg_setup.crc[0] = sum & 0xFFFF;