Simple subtraction

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- 11th July 2017, 21:33
Michael

Simple subtraction

There must be something wrong in my understanding of this but I'm simply trying to
decrement the value of a variable by 1.

This is part of the code and all the variables are bytes.

I'm using a temperature probe and when it gets to a preset temperature, LCD indicates ready.
All that is working fine but when I create a variable "cunder" that should be 1 degree less I don't get my high at portb.0

All the temp readings are fine etc -- lots of code I'm not showing -- but it must be "cunder".

Other languages I've used you can simply subtract a 1 like I did. (98 becomes 97 etc).

Thanks much for any help.

if (c = 1) and (CT >= tempsetc) then
high portb.3
cunder = (tempsetc - 1)
rdy = 1
LCDOUT $FE,1, " READY :)"
LCDOUT $FE,$C0," Press Start" 'all this works fine
endif

if (c = 1) and (ct <= cunder) then
high portb.0 'no high with my probe at lower temp
endif
- 12th July 2017, 06:37
richard

Re: Simple subtraction

this piece of code indicates that subtracting 1 from a var works as expected, providing vars are indeed bytes and no overflows occur

Code:

cunder var byte tempsetc var byte ct var byte ct=50 pause 2000 Debug "Start",13 ,10 for tempsetc = 1 to 255 cunder = (tempsetc - 1) Debug 13 ,10,"cunder = " ,#tempsetc," - 1 = ", #cunder if ct <= cunder then Debug 9, #ct ," <= ", #cunder else Debug 9, #ct ," > ", #cunder endif next stop

result

Code:

Start cunder = 1 - 1 = 0 50 > 0 cunder = 2 - 1 = 1 50 > 1 cunder = 3 - 1 = 2 50 > 2 cunder = 4 - 1 = 3 50 > 3 cunder = 5 - 1 = 4 50 > 4 cunder = 6 - 1 = 5 50 > 5 cunder = 7 - 1 = 6 50 > 6 cunder = 8 - 1 = 7 50 > 7 cunder = 9 - 1 = 8 50 > 8 cunder = 10 - 1 = 9 50 > 9 cunder = 11 - 1 = 10 50 > 10 cunder = 12 - 1 = 11 50 > 11 cunder = 13 - 1 = 12 50 > 12 cunder = 14 - 1 = 13 50 > 13 cunder = 15 - 1 = 14 50 > 14 cunder = 16 - 1 = 15 50 > 15 cunder = 17 - 1 = 16 50 > 16 cunder = 18 - 1 = 17 50 > 17 cunder = 19 - 1 = 18 50 > 18 cunder = 20 - 1 = 19 50 > 19 cunder = 21 - 1 = 20 50 > 20 cunder = 22 - 1 = 21 50 > 21 cunder = 23 - 1 = 22 50 > 22 cunder = 24 - 1 = 23 50 > 23 cunder = 25 - 1 = 24 50 > 24 cunder = 26 - 1 = 25 50 > 25 cunder = 27 - 1 = 26 50 > 26 cunder = 28 - 1 = 27 50 > 27 cunder = 29 - 1 = 28 50 > 28 cunder = 30 - 1 = 29 50 > 29 cunder = 31 - 1 = 30 50 > 30 cunder = 32 - 1 = 31 50 > 31 cunder = 33 - 1 = 32 50 > 32 cunder = 34 - 1 = 33 50 > 33 cunder = 35 - 1 = 34 50 > 34 cunder = 36 - 1 = 35 50 > 35 cunder = 37 - 1 = 36 50 > 36 cunder = 38 - 1 = 37 50 > 37 cunder = 39 - 1 = 38 50 > 38 cunder = 40 - 1 = 39 50 > 39 cunder = 41 - 1 = 40 50 > 40 cunder = 42 - 1 = 41 50 > 41 cunder = 43 - 1 = 42 50 > 42 cunder = 44 - 1 = 43 50 > 43 cunder = 45 - 1 = 44 50 > 44 cunder = 46 - 1 = 45 50 > 45 cunder = 47 - 1 = 46 50 > 46 cunder = 48 - 1 = 47 50 > 47 cunder = 49 - 1 = 48 50 > 48 cunder = 50 - 1 = 49 50 > 49 cunder = 51 - 1 = 50 50 <= 50 cunder = 52 - 1 = 51 50 <= 51 cunder = 53 - 1 = 52 50 <= 52 cunder = 54 - 1 = 53 50 <= 53 cunder = 55 - 1 = 54 50 <= 54 cunder = 56 - 1 = 55 50 <= 55 cunder = 57 - 1 = 56 50 <= 56 cunder = 58 - 1 = 57 50 <= 57 cunder = 59 - 1 = 58 50 <= 58 cunder = 60 - 1 = 59 50 <= 59 cunder = 61 - 1 = 60 50 <= 60 cunder = 62 - 1 = 61 50 <= 61 cunder = 63 - 1 = 62 50 <= 62 cunder = 64 - 1 = 63 50 <= 63 cunder = 65 - 1 = 64 50 <= 64 cunder = 66 - 1 = 65 50 <= 65 cunder = 67 - 1 = 66 50 <= 66 cunder = 68 - 1 = 67 50 <= 67 cunder = 69 - 1 = 68 50 <= 68 cunder = 70 - 1 = 69 50 <= 69 cunder = 71 - 1 = 70 50 <= 70 cunder = 72 - 1 = 71 50 <= 71 cunder = 73 - 1 = 72 50 <= 72 cunder = 74 - 1 = 73 50 <= 73 cunder = 75 - 1 = 74 50 <= 74 cunder = 76 - 1 = 75 50 <= 75 cunder = 77 - 1 = 76 50 <= 76 cunder = 78 - 1 = 77 50 <= 77 cunder = 79 - 1 = 78 50 <= 78 cunder = 80 - 1 = 79 50 <= 79 cunder = 81 - 1 = 80 50 <= 80 cunder = 82 - 1 = 81 50 <= 81 cunder = 83 - 1 = 82 50 <= 82 cunder = 84 - 1 = 83 50 <= 83 cunder = 85 - 1 = 84 50 <= 84 cunder = 86 - 1 = 85 50 <= 85 cunder = 87 - 1 = 86 50 <= 86 cunder = 88 - 1 = 87 50 <= 87 cunder = 89 - 1 = 88 50 <= 88 cunder = 90 - 1 = 89 50 <= 89 cunder = 91 - 1 = 90 50 <= 90 cunder = 92 - 1 = 91 50 <= 91 cunder = 93 - 1 = 92 50 <= 92 cunder = 94 - 1 = 93 50 <= 93 cunder = 95 - 1 = 94 50 <= 94 cunder = 96 - 1 = 95 50 <= 95 cunder = 97 - 1 = 96 50 <= 96 cunder = 98 - 1 = 97 50 <= 97 cunder = 99 - 1 = 98 50 <= 98 cunder = 100 - 1 = 99 50 <= 99 cunder = 101 - 1 = 100 50 <= 100 cunder = 102 - 1 = 101 50 <= 101 cunder = 103 - 1 = 102 50 <= 102 cunder = 104 - 1 = 103 50 <= 103 cunder = 105 - 1 = 104 50 <= 104 cunder = 106 - 1 = 105 50 <= 105 cunder = 107 - 1 = 106 50 <= 106 cunder = 108 - 1 = 107 50 <= 107 cunder = 109 - 1 = 108 50 <= 108 cunder = 110 - 1 = 109 50 <= 109 cunder = 111 - 1 = 110 50 <= 110 cunder = 112 - 1 = 111 50 <= 111 cunder = 113 - 1 = 112 50 <= 112 cunder = 114 - 1 = 113 50 <= 113 cunder = 115 - 1 = 114 50 <= 114 cunder = 116 - 1 = 115 50 <= 115 cunder = 117 - 1 = 116 50 <= 116 cunder = 118 - 1 = 117 50 <= 117 cunder = 119 - 1 = 118 50 <= 118 cunder = 120 - 1 = 119 50 <= 119 cunder = 121 - 1 = 120 50 <= 120 cunder = 122 - 1 = 121 50 <= 121 cunder = 123 - 1 = 122 50 <= 122 cunder = 124 - 1 = 123 50 <= 123 cunder = 125 - 1 = 124 50 <= 124 cunder = 126 - 1 = 125 50 <= 125 cunder = 127 - 1 = 126 50 <= 126 cunder = 128 - 1 = 127 50 <= 127 cunder = 129 - 1 = 128 50 <= 128 cunder = 130 - 1 = 129 50 <= 129 cunder = 131 - 1 = 130 50 <= 130 cunder = 132 - 1 = 131 50 <= 131 cunder = 133 - 1 = 132 50 <= 132 cunder = 134 - 1 = 133 50 <= 133 cunder = 135 - 1 = 134 50 <= 134 cunder = 136 - 1 = 135 50 <= 135 cunder = 137 - 1 = 136 50 <= 136 cunder = 138 - 1 = 137 50 <= 137 cunder = 139 - 1 = 138 50 <= 138 cunder = 140 - 1 = 139 50 <= 139 cunder = 141 - 1 = 140 50 <= 140 cunder = 142 - 1 = 141 50 <= 141 cunder = 143 - 1 = 142 50 <= 142 cunder = 144 - 1 = 143 50 <= 143 cunder = 145 - 1 = 144 50 <= 144 cunder = 146 - 1 = 145 50 <= 145 cunder = 147 - 1 = 146 50 <= 146 cunder = 148 - 1 = 147 50 <= 147 cunder = 149 - 1 = 148 50 <= 148 cunder = 150 - 1 = 149 50 <= 149 cunder = 151 - 1 = 150 50 <= 150 cunder = 152 - 1 = 151 50 <= 151 cunder = 153 - 1 = 152 50 <= 152 cunder = 154 - 1 = 153 50 <= 153 cunder = 155 - 1 = 154 50 <= 154 cunder = 156 - 1 = 155 50 <= 155 cunder = 157 - 1 = 156 50 <= 156 cunder = 158 - 1 = 157 50 <= 157 cunder = 159 - 1 = 158 50 <= 158 cunder = 160 - 1 = 159 50 <= 159 cunder = 161 - 1 = 160 50 <= 160 cunder = 162 - 1 = 161 50 <= 161 cunder = 163 - 1 = 162 50 <= 162 cunder = 164 - 1 = 163 50 <= 163 cunder = 165 - 1 = 164 50 <= 164 cunder = 166 - 1 = 165 50 <= 165 cunder = 167 - 1 = 166 50 <= 166 cunder = 168 - 1 = 167 50 <= 167 cunder = 169 - 1 = 168 50 <= 168 cunder = 170 - 1 = 169 50 <= 169 cunder = 171 - 1 = 170 50 <= 170 cunder = 172 - 1 = 171 50 <= 171 cunder = 173 - 1 = 172 50 <= 172 cunder = 174 - 1 = 173 50 <= 173 cunder = 175 - 1 = 174 50 <= 174 cunder = 176 - 1 = 175 50 <= 175 cunder = 177 - 1 = 176 50 <= 176 cunder = 178 - 1 = 177 50 <= 177 cunder = 179 - 1 = 178 50 <= 178 cunder = 180 - 1 = 179 50 <= 179 cunder = 181 - 1 = 180 50 <= 180 cunder = 182 - 1 = 181 50 <= 181 cunder = 183 - 1 = 182 50 <= 182 cunder = 184 - 1 = 183 50 <= 183 cunder = 185 - 1 = 184 50 <= 184 cunder = 186 - 1 = 185 50 <= 185 cunder = 187 - 1 = 186 50 <= 186 cunder = 188 - 1 = 187 50 <= 187 cunder = 189 - 1 = 188 50 <= 188 cunder = 190 - 1 = 189 50 <= 189 cunder = 191 - 1 = 190 50 <= 190 cunder = 192 - 1 = 191 50 <= 191 cunder = 193 - 1 = 192 50 <= 192 cunder = 194 - 1 = 193 50 <= 193 cunder = 195 - 1 = 194 50 <= 194 cunder = 196 - 1 = 195 50 <= 195 cunder = 197 - 1 = 196 50 <= 196 cunder = 198 - 1 = 197 50 <= 197 cunder = 199 - 1 = 198 50 <= 198 cunder = 200 - 1 = 199 50 <= 199 cunder = 201 - 1 = 200 50 <= 200 cunder = 202 - 1 = 201 50 <= 201 cunder = 203 - 1 = 202 50 <= 202 cunder = 204 - 1 = 203 50 <= 203 cunder = 205 - 1 = 204 50 <= 204 cunder = 206 - 1 = 205 50 <= 205 cunder = 207 - 1 = 206 50 <= 206 cunder = 208 - 1 = 207 50 <= 207 cunder = 209 - 1 = 208 50 <= 208 cunder = 210 - 1 = 209 50 <= 209 cunder = 211 - 1 = 210 50 <= 210 cunder = 212 - 1 = 211 50 <= 211 cunder = 213 - 1 = 212 50 <= 212 cunder = 214 - 1 = 213 50 <= 213 cunder = 215 - 1 = 214 50 <= 214 cunder = 216 - 1 = 215 50 <= 215 cunder = 217 - 1 = 216 50 <= 216 cunder = 218 - 1 = 217 50 <= 217 cunder = 219 - 1 = 218 50 <= 218 cunder = 220 - 1 = 219 50 <= 219 cunder = 221 - 1 = 220 50 <= 220 cunder = 222 - 1 = 221 50 <= 221 cunder = 223 - 1 = 222 50 <= 222 cunder = 224 - 1 = 223 50 <= 223 cunder = 225 - 1 = 224 50 <= 224 cunder = 226 - 1 = 225 50 <= 225 cunder = 227 - 1 = 226 50 <= 226 cunder = 228 - 1 = 227 50 <= 227 cunder = 229 - 1 = 228 50 <= 228 cunder = 230 - 1 = 229 50 <= 229 cunder = 231 - 1 = 230 50 <= 230 cunder = 232 - 1 = 231 50 <= 231 cunder = 233 - 1 = 232 50 <= 232 cunder = 234 - 1 = 233 50 <= 233 cunder = 235 - 1 = 234 50 <= 234 cunder = 236 - 1 = 235 50 <= 235 cunder = 237 - 1 = 236 50 <= 236 cunder = 238 - 1 = 237 50 <= 237 cunder = 239 - 1 = 238 50 <= 238 cunder = 240 - 1 = 239 50 <= 239 cunder = 241 - 1 = 240 50 <= 240 cunder = 242 - 1 = 241 50 <= 241 cunder = 243 - 1 = 242 50 <= 242 cunder = 244 - 1 = 243 50 <= 243 cunder = 245 - 1 = 244 50 <= 244 cunder = 246 - 1 = 245 50 <= 245 cunder = 247 - 1 = 246 50 <= 246 cunder = 248 - 1 = 247 50 <= 247 cunder = 249 - 1 = 248 50 <= 248 cunder = 250 - 1 = 249 50 <= 249 cunder = 251 - 1 = 250 50 <= 250 cunder = 252 - 1 = 251 50 <= 251 cunder = 253 - 1 = 252 50 <= 252 cunder = 254 - 1 = 253 50 <= 253 cunder = 255 - 1 = 254 50 <= 254

the problem lies elsewhere

you need to provide a compliable example that demonstrates the problem
- 12th July 2017, 12:25
Scampy

Re: Simple subtraction

Michael, it might be handy if you posted all your code so we could see how the rest of it is meant to work - you need to use the [ CODE ] and [ / CODE ] (with out spaces inside the brackets) to make it clearer.

I use the following to read a DS18B20 temperature probe and display the temperature on an LCD. I then have the routine below to trigger a pin that drives a fan when the temperature exceeds a set value - you could always change the > for < to trigger the condition you want

Code:

'******************************************************************************* 'Get and display the temperature GIE = 0 ' turn off interupts owin DQ, 1, [],NoDevice ' pole 1 wire bus - if no responce then device not pressent OWOUT DQ, 1, [$CC, $44] ' Start temperature conversion OWOUT DQ, 1, [$CC, $BE] ' Read the temperature OWIN DQ, 0, [temperature.LOWBYTE, temperature.HIGHBYTE] GIE = 1 ' turn interupts back on temperature = temperature */ 1600 lcdout $FE,$D4+0,"TEMP ",dec(temperature / 100),$DF,"C" '******************************************************************************* ' fan:'check to see if fan is needed fantrigger=fanset if (temperature / 100)> fantrigger then high portA.4 endif
- 12th July 2017, 14:10
HenrikOlsson

Re: Simple subtraction

And remember that BYTEs and WORDS are unsigned so doing something like a "less than 0" will never ever return true because a BYTE or WORD will always be 0 or more in that context.

/Henrik.
- 12th July 2017, 14:36
Michael

Re: Simple subtraction

Ok thanks -- I'll look at it closer -- at least I know it should work with a minus 1.

I use Micro code studio by the way. Is there another IDE that is straightforward like it is but has a few more features? For example, you can't even comment out a block of code, just individual lines.

Also, I have never really had any experience with simulators. My Picbasic interest sort of peaked 20 years ago (although I still think it's fantastic) and back then simulation was a bad word.

Be nice if they came up with something that could scroll through your code and detect operational errors. ?
- 12th July 2017, 15:05
Michael

Re: Simple subtraction

Here comes a dumb question --

var1 = word
var2 = byte

var1 = 2
var2 = 3

Can't you compare a word to a byte?

If var1 <= var2 then
do this

It's in my head that a word is a number with the capability of larger numbers but also higher resolution for smaller numbers?
(More decimal places?) So a 2 as a word variable is the same as a byte.

Wrong? Do I need to use var.highbyte instead ? (hobbyist -- so I forget this stuff).
- 12th July 2017, 15:26
Art

Re: Simple subtraction

You can use a word somewhat like a float, but essentially, I believe you can compare those two types.
Even if they didn’t directly compare, you could compare the byte to the lower word byte, and if the upper word byte is zero,
the first compare with he lower byte is valid. otherwise if the upper word byte is not zero, the word is higher.
- 12th July 2017, 16:36
HenrikOlsson

Re: Simple subtraction

In PBP all variable types stores integer values only so only the size of the number they can hold changes. The resolution is always the same.
I see no, and don't know of any, issues with comparing a BYTE to WORD or the other way around but again remember that BYTES and WORDS are always unsigned integers so a variable containing 253 will be smaller than a BYTE (or WORD) variable containin the result of 100-101.

/Henrik.
- 12th July 2017, 20:07
aerostar

Re: Simple subtraction

Quote:

Originally Posted by Michael

Ok thanks -- I'll look at it closer -- at least I know it should work with a minus 1.

I use Micro code studio by the way. Is there another IDE that is straightforward like it is but has a few more features? For example, you can't even comment out a block of code, just individual lines.

Hightlite the block of code, then click comment - all lines will then be commented out - same in reverse to uncomment