Converting to ASCII in C
Using a microcontroller (PIC18F4580), I need to collect data and send it to an SD card for later analysis. The data it collects will have values between 0 and 1023, or 0x0 and 0x3FF.
So what I need to do is convert 1023 into a base 10 string of literal ASCII values (0x31, 0x30, 0x32, 0x33, ...).
My problem is that the only way I can think of to split the digits apart requires a lot of division.
char temp[4];
temp[0] = 1023 % 10;
temp[1] = (1023 % 100) / 10;
temp[2] = (1023 % 1000) / 100;
temp[3] = (1023 % 10000) / 1000;
Using this method, finding the ASCII values of an n digit decimal number requires 2n-1 divisions. Is there a method that would be faster?
The end goal of this is to wind up with a .csv file on the SD card that can quickly be plugged into any laptop to see a graph of the data in Excel.
Answer
The obvious solution is not to convert the data to ASCII at all but store it in binary format. That way all you need to worry about is the endianness of the data. If the system performing the later analysis is far more powerful than your embedded target, then it would make sense to let that deal with the conversion and and byte order.
On the other hand, it is possible that the execution time of the / and % is insignificant compared to the time taken to transfer the data to the SD card; so make sure that you are optimising the right thing.