Even as an embedded C developer I use "idx" and "count" instead of "i". Not just because I'm a member of the "slightly longer but more descriptive names are better" gang, but also for searchability. If I'm trying to track down where an array is accessed in a loop, for example, "idx" is more likely to take me only to the results I'm looking for and not also the "i" in int8_t or whatever.