As @erenfro correctly noted, this isn't a bit width issue, as both int and long are 32 bit on Xtensa. The “word” type is a total fail. char vs signed char vs unsigned char. Or perhaps there's a better way. Unsigned long variables are extended size variables for number storage and store 32 bits (4 bytes). In the Arduino int type (which is signed), if the high bit is a "1", the number is interpreted as a negative number, and the other 15 bits are interpreted with (2’s complement math). I want to reinterpret the 32 bits of an unsigned long as a signed long. But the size of uint32_t is always 32 bits independent of convention the compiler is following.. It's 64bits on ARM, and only 32 (the same as "float") on AVR. Am I wrong? I'm using an unsigned long … (Less plausibly, it could be unsigned char or unsigned short on an unusual system, or it could be an extended integer type; it cannot be unsigned long long, which is at least 64 bits wide.) int infrared1 = A0; int infrared2 = A1; #define button 9 int color,number,number1,number2; unsigned long firstMillis1; unsigned long firstMillis2; unsigned long secondMillis1; You may use long type also for inet_addr() function since most of the architecture use 32 bits(4 bytes) for long type but it is not always applicable . "double" is also a different size on ARM vs AVR. If you don’t, the result of the subtraction will become negative if given the right input. uint16_t and uint32_t (the same as unsigned long on You are likely wondering what are uint8_t, uint16_t, uint32_t and uint64_t. Some architecture use 64 bits for long type..LP64 convention use 64 bits for long type. Unlike standard longs, unsigned longs will not store negative numbers, making their range from 0 to 4,294,967,295 (2^32 - 1). The difference between unsigned ints and (signed) ints, lies in the way the highest bit, sometimes referred to as the "sign" bit, is interpreted. However in C++ int and long are different types, even if they are of the same size. So it COMMON for char to be 8bits, int to be either 16 or 32, and long to 32. // frequency is a double int32_t freq = frequency * 4294967296 / 180.0e6; That calculation is going to be done using floating point arithmetic. So the only way to allow libraries to be portable between ESP32 Arduino core and other cores is to use unsigned long for the return value. and NEVER use the Arduino type “word” as that is defined to be “unsigned short” which is 16 bits on AVR and 32 bits on ARM and pic32. Example Unsigned Long velocity = 101006 ;// declaration of variable with type Unsigned Long and initialize it with 101006 "long" has almost always been 32bits. It could plausibly be either unsigned int or unsigned long int. That's a good question. The library uses: uint8_t and uint16_t Until now I am only used of using the int and unsigned int (data types as described in the arduino … I would discourage using the “cutsie” Arduino types like byte. Because it could be really helpul! Hello, I am trying to modify a library at the moment. I don't think simply casting it to long will do the trick. Modern programmers should use the standardized explicit-size types instead: uin8_t, int16_t, uint32_t, etc. But what are ranges of all these types? Which means that your fancy magic number on the right hand side is going to be truncated to about 6 decimal digits of precision anyway. Printing a uint32_t value with "%u" is non-portable. 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