ATMEGA328p convert analog value to voltage
This is an extract of the official ATMEGA328p data sheet page 261:
As the documentation say
Vin * 1024
ADC = ----------
Vref
What I don't understand is an analog pin can provide us 10bits. That's mean a value between 0x0 and 0x3ff (1023)
So I don't understand why the documentation say Vin * 1024 and not 1023. Because for me 0v = 0 and 5v = 1023?
Yeah this is a common mistake. One thinks 10 bits = 2^10 = 1024 and so there will be 1024 steps, right? Nope, 10 bit ADCs only give output up to 1023 (3FFh), because that is the largest number you can fit into 10 bits.
So if you do arithmetic on 1024 instead of 1023, you introduce a very slight inaccuracy in the calculation. I've done this bug myself and it sat in production code for over 10 years without anyone noticing, and when I fixed the bug nobody noticed a difference either :) But naturally we should always strive for program correctness.
- Simple frame by frame video decoder library
- GCC no longer implements <varargs.h>
- Contents of IO buffer unknown == unsafe?
- Avoiding strcpy overflow destination warning
- Sort program not working, not sure why
- Fast & accurate atan/arctan approximation algorithm
- What's the difference between strtok_r and strtok_s in C?
- How memory address for pointer to arrays is same as an element in 2D array?
- Which is the best way to suppress "unused variable" warning
- How to use ellipsis in c's case statement?
- How can I exclude non-numeric keys? CS50 Caesar Pset2
- Fast ceiling of an integer division in C / C++
- Is there an invalid pthread_t id?
- How to Implement Universal Setter/Getter Functions for Interrupt-Driven Variables in Embedded C?
- How does SIMD (avx) processing work? for example, if I want 10 32 bit floats how do i fit in a 256 bit avx vector?
- FDCAN problems on STM32G4
- How does the call macro enable mutual recursion between functions f and g in this Hanoi Tower implementation?
- Running test on Rocket core CPU - global variable initialized to 0 is unsuccessful, output wrong value instead
- Interacting with C arrays without knowing the size
- Combination of two strings
- carriage return by fgets
- How to use special characters in C?
- Why does 1.0/100.0 == 0.1/10.0 give True?
- Is it correct to compare pointers in C?
- Force free() to return malloc memory back to OS
- How can I print to standard error in C with 'printf'?
- What is the standard behavior of fread in C on Windows?
- How is strtok removing lines it shouldn't have access to?
- Using array as smart point in C
- Assigning string to malloced 2d char array not working as intended