Electronic – AVR ATMEGA644 print Local time

atmegaavr

From this tutorial, I can print local time when I code using codeblock.
https://www.tutorialspoint.com/c_standard_library/c_function_localtime.htm

I am measuring capacitance by atmega644. I read the capacitance data from the ADC and print it. I want to add the local time so that I can know how much is the capacitance at a specific time.

I try the exact same thing of this tutorial and get the following errors. How can I print local time along with my continuous capacitance measurement?

Best Answer

The full C library is not available on embedded devices. Consult the avr-libc manual to see what's available.

In practice, if you want a real-time clock on an ATmega microcontroller, you will probably need to implement it yourself using a timer configured to fire once per second. (This will also mean you will need some way for the user to set the current time.)

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Electronic – Help understanding AVR execution timing

This is a bad approach. Ideally you would measure a very large number of NOP commands - say, one million - instead of just one. I think that's the first foolish thing I can find. I would not be very surprised if your number changes right after you implement that change.

Also, can you view the disassembly of your C code? I wouldn't even try to judge the timing without seeing exactly what assembly code was generated from my C code. I would try to work backwards from the assembly to calculate what the execution time should be (via the instruction set manual you found). That way you can see if the scope measurement is off by a little or by a lot. A little might mean you made a math error. A lot might mean one of your assumptions is wrong.

Electronic – How to use AVR ADC with multiplier

int can only be 0-255

That's not correct. In the C programming language, an int is always at least 16 bits wide, even on 8-bit micros. A char is 8 bits wide.

But when using inttypes.h, I strongly recommend using the explicit types like uint8_t,int16_t or uint32_t.

Your real error is using _delay_ms() with a variable parameter. This is not allowed, as it is a macro involving floating point calculations - at least in avr gcc. You are supposed to use something like this:

void DelayMs(int delay) {
  while(delay--) _delay_ms(1);
}

Best Answer

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