The compiler seems to have trouble with the equation below for SpdRngPC when input is variables or from calculated constants.
No_Var gives correct result = 64
This reason a cast is required is the range of the result of the calculation is 255 to 650.
When
Motor_Spd 255
MaxPC 255
MinPC 0
= 650 Result is 650 so therefore a WORD cast is required.
When
Motor_Spd 0
MaxPC 0
MinPC 255
= 255
and, further proof - the calc (Motor_Spd*(MaxPC-MinPC)) would overflow the temp variable unless you cast the temp variable result. The max result of this calc is 65025... a word.
Last edit: Anobium 2022-12-30
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That works. Thanks
I was misunderstanding that if I had a word variable (SpdRngPC) the calculation would be done as word.
because this worked Temp1 = (Motor_Spd*(MaxPC-MinPC)) = 5520 I wrongly assumed the full calc was the same.
I will be limiting the input values 0 - 100 %
Liv&Lern
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As MaxPC-MinPC could be a negative, in theory. So, the extra cast would increase realibiilty but a check of the variables prior to the calculation would be faster to execute - then, you could remove the [INTEGER].
:-)
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Starting a new thread...
The compiler seems to have trouble with the equation below for SpdRngPC when input is variables or from calculated constants.
No_Var gives correct result = 64
If I break it up then it calculates correct, Temp3 = 64.
Tried both PIC & AVR, on simulator & real hardware.
Please try changing the code to use a [CAST] as follows:
SpdRngPC = ([WORD]Motor_Spd*(MaxPC-MinPC)/100)+MinPCThis reason a cast is required is the range of the result of the calculation is 255 to 650.
When
Motor_Spd 255
MaxPC 255
MinPC 0
= 650 Result is 650 so therefore a WORD cast is required.
When
Motor_Spd 0
MaxPC 0
MinPC 255
= 255
and, further proof - the calc
(Motor_Spd*(MaxPC-MinPC))would overflow the temp variable unless you cast the temp variable result. The max result of this calc is 65025... a word.Last edit: Anobium 2022-12-30
That works. Thanks
I was misunderstanding that if I had a word variable (SpdRngPC) the calculation would be done as word.
because this worked
Temp1 = (Motor_Spd*(MaxPC-MinPC))= 5520 I wrongly assumed the full calc was the same.I will be limiting the input values 0 - 100 %
Liv&Lern
No problem.
Actually, the reliable coding would be:
As
MaxPC-MinPCcould be a negative, in theory. So, the extra cast would increase realibiilty but a check of the variables prior to the calculation would be faster to execute - then, you could remove the[INTEGER].:-)