diff --git a/src/monocoque/devices/serial/moza.c b/src/monocoque/devices/serial/moza.c
index 0108148..f98f5d3 100644
--- a/src/monocoque/devices/serial/moza.c
+++ b/src/monocoque/devices/serial/moza.c
@@ -13,67 +13,64 @@
 #define MOZA_SERIAL_TEMPLATE {0x7e, 0x06, 0x41, 0x13, 0xfd, 0xde, 0x0, 0x0, 0x0, 0x0, 0x0}
 #define MOZA_NUM_AVAILABLE_LEDS 10
 #define MOZA_BLINKING_BIT 7
+#define MOZA_PAYLOAD_SIZE 11
 #define MOZA_MAGIC_VALUE 0x0d
 #define BIT(nr) (1UL << (nr))
 
 unsigned char moza_checksum(unsigned char *data)
 {
     unsigned char ret = MOZA_MAGIC_VALUE;
-    for (short i = 0; i < sizeof(data)/sizeof(data[0]); i++)
+    for (short i = 0; i < MOZA_PAYLOAD_SIZE; i++)
     {
         ret += data[i];
     }
 
-    return ret;
+    return ret % 0x100;
 }
 
 int moza_update(SerialDevice* serialdevice, unsigned short maxrpm, unsigned short rpm)
 {
     unsigned char bytes[] = MOZA_SERIAL_TEMPLATE;
-    int size = sizeof(bytes)/sizeof(bytes[0]);
-
+    int size = MOZA_PAYLOAD_SIZE;
     float perct = (float)rpm/(float)maxrpm;
 
-    if (perct >= 0.8)
+    if (perct >= .1)
         bytes[9] |= BIT(0);
 
-    if (perct >= 0.83)
+    if (perct >= .2)
         bytes[9] |= BIT(1);
 
-    if (perct >= 0.86)
+    if (perct >= .3)
         bytes[9] |= BIT(2);
 
-    if (perct >= 0.89)
+    if (perct >= .4)
         bytes[9] |= BIT(3);
 
-    if (perct >= 0.91)
-        bytes[8] |= BIT(4);
+    if (perct >= .5)
+        bytes[9] |= BIT(4);
 
-    if (perct >= 0.92)
-        bytes[8] |= BIT(5);
+    if (perct >= .6)
+        bytes[9] |= BIT(4);
 
-    if (perct >= 0.93)
+    if (perct >= .7)
+        bytes[9] |= BIT(5);
+
+    if (perct >= .8)
         bytes[8] |= BIT(6);
 
-    if (perct >= 0.94)
+    if (perct >= .9)
         bytes[8] |= BIT(7);
 
-    if (perct >= 0.96)
-        bytes[8] |= BIT(0);
-
-    if (perct >= 0.96)
-        bytes[8] |= BIT(1);
-
     // blinking
-    if (perct >= 0.97)
-        bytes[9] |= BIT(MOZA_BLINKING_BIT);
+    if (perct >= .95)
+        bytes[8] |= BIT(MOZA_BLINKING_BIT);
 
     bytes[10] = moza_checksum(bytes);
 
     int result = 1;
     if (serialdevice->port)
     {
-        slogd("copying %i bytes to moza device", size);
+        slogd("copying %i bytes to moza device", MOZA_PAYLOAD_SIZE);
         slogt("writing bytes %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x from rpm %i maxrpm %i", bytes[0], bytes[1], bytes[2], bytes[3], bytes[4], bytes[5], bytes[6], bytes[7], bytes[8], bytes[9], bytes[10], rpm, maxrpm);
         result = monocoque_serial_write(serialdevice->id, bytes, size, MOZA_TIMEOUT);
     }