Converting from void * to float - pointers

Question

I have a pointer to some location in memory passed in, void *dataLoc.
Some program is transferring memory there as a bunch of unsigned chars where 0x00 is 0 and 0xFF is one.
I want to be able to pull, say, every 4th char and convert it to the float of what number is supposed to be represented. But I'm having trouble understanding how I get from a void * to an array of char[] to an array of float[].
My initial thought was to do something like
for(i=0,i<100,i++){
floatArray[i] = (float)(*((unsigned char *)dataLoc[4*i])) / 255;
}
the void * is cast to a char *.
the next 4th char is selected from the for loop
the * dereferences the char pointer, which should give me an unsigned char,
the float should change the char into a float, but a float representation of the number I want *255
I divide by 255 to get the fraction I want.
This fails, because I get the error "pointer of type 'void ' used in arithmetic
'void' is not a pointer-to-object type and beyond this, I'm not really confident that the rest of that line will work out the way I would like.
Can someone advise the proper way to handle this?

Answer 1

Good that you had warnings enabled.
dataLoc[4*i] occurs before (unsigned char *)dataLoc and leads to "pointer of type 'void *' used in arithmetic ..."
Cast to unsigned char * first.
Also remove extra level of *. The following is type unsigned char
((unsigned char *)dataLoc)[4*i]
Fixed:
void * dataLoc;
float floatArray[100];
// for(i=0,i<100,i++){ Use ';', not ','
for(int i=0;i<100;i++){
// Cast to `unsigned char *` before using `[]`
// * not needed here ---v
floatArray[i] = (float)( ( ((unsigned char *)dataLoc) [4*i])) / 255;
}
or
for (int i=0; i<100 ;i++) {
unsigned char value = ((unsigned char *)dataLoc)[4*i];
floatArray[i] = value / 255.0f;
}