How to properly combine 4 bytes to make a float (single) - c

Question

I have the following:
payload.data[i].data = (buf[8] << 24) | (buf[9] << 16) | (buf[10] << 8) | (buf[11]);
note: payload.data[i].dataif of type float.
Using this: printf("test:%X%X%X%X", buf[8], buf[9], buf[10], buf[11]);, I have confirmed that the buffer contains #42C78A3D or DEC 99.77 (roughly).
This: printf("Float value:%f", payload.data[i].data prints out 1120373248.00, which is DEC for #42C78A00
It seems to me that for some reason, buf[11] is coming up empty.
Here is a more complete view of my code:
int i = 0;
int j = 0;
struct sensor_payload payload;
payload.key = (buf[0] << 8) | buf[1];
payload.id = (buf[2] << 8) | buf[3];
payload.type = (buf[4] << 8) | buf[5];
payload.fields = buf[6];
for(i = 0, j = 0; i < payload.fields; i++, j = j +33){
payload.data[i].data_type = buf[j+7];
payload.data[i].data = (buf[j+8] << 24) | (buf[j+9] << 16) | (buf[j+10] << 8) | (buf[j+11]);
slog(0, SLOG_DEBUG, "test:%X%X%X%X", buf[8], buf[9], buf[10], buf[11]);
}
payload.valid = true;
return payload;
and the definitions:
struct sensor_data{
uint8_t data_type;
float data;
};
struct sensor_payload{
uint16_t key, id, type;
uint8_t fields;
struct sensor_data data[4];
bool valid;
};

Answer 1

There's a lot in you code which is unclear. However, the only discrepancy I see is that you're putting index-offset entries into your data (notice the j+x pattern):
(buf[j+8] << 24) | (buf[j+9] << 16) | (buf[j+10] << 8) | (buf[j+11])
while printing non-offset entires:
slog(0, SLOG_DEBUG, "test:%X%X%X%X", buf[8], buf[9], buf[10], buf[11])
Technically, data you're printing and putting into the float is only the same for i==0.