Calculation with preprocessor-defines yields incorrect value - c

Question

I am pretty sure it is a common mistake of a beginner but I don't know the correct words for finding an existing answer.
I have defined some consecutive preprocessor macros:
#define DURATION 10000
#define NUMPIXELS 60
#define NUMTRANSITION 15
#define UNITS_PER_PIXEL 128
#define R ((NUMPIXELS-1)/2 + NUMTRANSITION) * UNITS_PER_PIXEL
Later I use these values to calculate a value and assign it to a variable. Here two examples:
// example 1
uint16_t temp; // ranges from 500 to 10000
temp = 255 * (temp - 500) / (10000 - 500);
Here, temp is always 0. Since my guess was/is an issue with the datatype, I also tried uint32_t temp. However, temp was always 255 in this case.
// example 2
uint32_t h = millis() + offset - t0 * R / DURATION;
millis() returns an increasing unsigned long value (milliseconds since the start). Here, h increases a factor of 4 too fast. The same for unsigned long h. When I tried a workaround by dividing by 4*DURATION, h was always 0.
Is it an datatype issue? If or if not, how can I solve it?

Answer 1

This code works on Arduino Uno and an ESP32 as expected
#define DURATION 10000
#define NUMPIXELS 60
#define NUMTRANSITION 15
#define UNITS_PER_PIXEL 128
#define R ((NUMPIXELS-1)/2 + NUMTRANSITION) * UNITS_PER_PIXEL
uint32_t t0 = millis();
void setup() {
// put your setup code here, to run once:
Serial.begin (115200);
//Later I use these values to calculate a value and assign it to a variable. Here two examples:
// example 1
randomSeed(721);
}
void loop() {
// For UNO /ESP use uint16_t temp = random(500,10000); // ranges from 500 to 10000
// for ATtiny85 (DigiSpark)
uint32_t temp = random(500,10000); // ranges from 500 to 10000
temp = 255 * (temp - 500) / (10000 - 500);
// Here, temp is always 0. Since my guess was / is an issue with the datatype, I also tried uint32_t temp. However, temp was always 255 in this case.
// example 2
Serial.println(temp);
uint16_t offset = random(2000, 5000);
uint32_t h = millis() + offset - t0 * R / DURATION;
Serial.println(h);
delay (5000); // Only to prevent too much Serial data, never use in production
}
Environment ArduinoIDE 1.8.12/ avr core 1.8.2 and ESP32 1.04. What hardware are you compiling to? Try the test program, it does (at least on the tested hardware) what it should.
EDIT: For reference OP uses Attiny85 (Digispark) where var size defs are more critical than on UNO /ESP -instead of Serial you would use SerialUSB. Tip for future support requesters -> always reference your environment (HW & SW) with microcontrollers because of possible hardware specific issues