Simple subtraction [Archive] - MEL PICBASIC Forum

Michael

- 11th July 2017, 21:33

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

richard

- 12th July 2017, 06:37

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

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

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

Scampy

- 12th July 2017, 12:25

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

'************************************************* ******************************
'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

HenrikOlsson

- 12th July 2017, 14:10

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.

Michael

- 12th July 2017, 14:36

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. ?

Michael

- 12th July 2017, 15:05

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).

Art

- 12th July 2017, 15:26

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.

HenrikOlsson

- 12th July 2017, 16:36

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.

aerostar

- 12th July 2017, 20:07