Lookup Tables

Hello
More dumb questions.
First, If i create a constant mice CON 3 where is that stored? Is it in eprom, ram, or flash program space. I assume it is stored in the flash program memory.

Second, if that constant is stored in the flash program memory then in theory I could make constants untill the device flash program memory is full.

What I am trying to do is make a look up table to read a thermistor. Yes I know use a lm34 or lm35 temp sensor. I've done that and they are awesome, but I am looking for cheap and not real accurate.

I have a chart made for a 10K thermistor that shows what adc value correlates to what temp. I have a 1024 different values and I am trying to figure out if a lookup table would work.

Third, if your still reading. How do I create a table in PBP? The book is pretty short and I can not find a darn thing in the forum.
Thanks
Nick

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I have a 1024 different values

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That is doable with an 18Fxxx chip.

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How do I create a table in PBP?

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Not sue what you mean? By typing?
Here is an example

Code:

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'Lets say
TXI = 255
GOSUB D_INDEX
' Now TXIU will hold the value 2500

D_INDEX:
'THERMO TEMPERATURES
LOOKUP2 TXI,[2500,2490,2480,2470,2460,2450,2440,2430,2420,2410,2400,2390,2380,2370,_
2360,2350,2340,2330,2320,2310,2300,2290,2280,2270,2260,2250,2240,2230,2220,2210,2200,_
2190,2180,2170,2160,2150,2140,2130,2120,2110,2100,2090,2080,2070,2060,2050,2040,2030,_
2020,2010,2000,1990,1980,1970,1960,1950,1940,1930,1920,1910,1900,1890,1880,1870,1860,_
1850,1840,1830,1820,1810,1800,1790,1780,1770,1760,1750,1740,1730,1720,1710,1700,1690,_
1680,1670,1660,1650,1640,1630,1620,1610,1600,1590,1580,1570,1560,1550,1540,1530,1520,_
1510,1500,1490,1480,1470,1460,1450,1440,1430,1420,1410,1400,1390,1380,1370,1360,1350,_
1340,1330,1320,1310,1300,1290,1280,1270,1260,1250,1240,1230,1220,1210,1200,1190,1180,_
1170,1160,1150,1140,1130,1120,1110,1100,1090,1080,1070,1060,1050,1040,1030,1020,1010,_
1000,990,980,970,960,950,940,930,920,910,900,890,880,870,860,850,840,830,820,810,800,_
790,780,770,760,750,740,730,720,710,700,690,680,670,660,650,640,630,620,610,600,590,_
580,570,560,550,540,530,520,510,_
500],TXIU
RETURN

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Dave, is it with the last version of PBP that you can use 1024 variables in lookup2 table?
With mine I am limited to 256 for 18fxxxx

Since your table is linear, with these two lines of code you can do without the rather large table:

If TXI > 200 Then TXI = 0
TXIU = 2500 - (TXI * 10)


Checking the regression of your data, most of the time you discover that you can do without the lookup table.

Nick, post your thermistor table convertion and I will check if it is feasible.

Cheers

Al.

I can not remember if 2.50 had 1024 constants. I have not used all 1024 but around 500 or so works with 2.60.

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Since your table is linear,

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Thanks for pointing that out, it may save someone some confusion.
That probably was not the best example.. Grabbed it from a piece of code that had a non-liner LOOKDOWN feeding the LOOKUP. I was playing with a "K" thermocouple and the reference/junction temperature..

Code:

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LOOKDOWN2 TX,>[898,895,892,889,886,883,879,876,873,870,867,863,860,857,854,850,_
847,844,841,838,835,832,828,825,822,819,815,812,809,805,802,799,795,792,788,785,_
782,778,775,772,769,765,762,758,755,751,748,744,741,737,734,731,727,724,721,717,_
713,710,706,703,699,696,692,689,685,682,678,675,671,667,664,660,656,653,650,646,_
643,639,635,632,628,624,620,617,614,610,606,603,599,595,592,588,584,580,577,573,_
570,566,562,558,555,551,547,544,540,536,532,529,525,521,517,513,509,506,502,498,_
495,491,487,483,479,475,471,468,464,460,456,453,449,445,441,437,433,429,426,422,_
418,414,410,406,402,398,395,391,387,383,379,375,371,367,363,360,356,352,348,344,_
340,336,332,328,324,321,317,313,309,305,301,297,293,290,286,282,278,274,270,267,_
263,259,255,252,248,244,240,236,232,229,224,221,217,213,209,206,202,198,194,190,_
187,183,180,176,173],TXI

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Have you considered the MCP9700 temp sensor from Microchip.
About to use one on a project myself, Cheap £0.22 @10off in farnell and hopefuly a lot less coding than a Thermistor.

Thanks guys for posting.
That helped me understand the lookup table.
Would it be faster and take up less code if I placed the table inside of an eeprom. Also to get the resolution I want over the temp. range I want, I think I am going to switch to a mcp 3202 12bit ad chip.

Another question for ya all. If I am reading a temp of 70.8 is it possible to store that in a 1 byte memory location. How I handle this now is to put the 70 in the high byte of a word variable and I put the .8 in the low byte.This works very well but doubles the memory requirments.

Thanks to You all
Nick

A correction to my not so good example

Code:

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'Lets say
TXI = 0
GOSUB D_INDEX
' Now TXIU will hold the value 2500

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" If Index is zero, Var is set to the first Value."

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Would it be faster and take up less code if I placed the table inside of an eeprom.

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Faster-- No, it takes time to read the EEPROM. Less code-- Probably yes.

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If I am reading a temp of 70.8 is it possible to store that in a 1 byte memory location.

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Not that I can think of.

Storing 1024 WORD values in LOOKUP2 statements would take over 8K words of program space.

But using the technique described here ... http://www.picbasic.co.uk/forum/show...php?t=3891#LAB
You can do it with just over 1K.

Faster, smaller, no external parts.