'
' K-type thermocouple conversion using MCP342x ADC and DS18B20 for coldjunction compensation
'
cpu 48
option explicit
option default integer
const ADCBits16=&B10001000
const ADCbits16timeout= 15
'max voltages gain 8 = +/- 0.256V
const signed=1
const unsigned=0
const zeroOffset=90 'the thermocouple table starts at -90 degrees C so we offset the table lookup by this
' Pin assignment
const DS18B20pin=26
const ADCi2c = &B1101000 ' set to match your hardware, NB base address is same as DS1307
'
dim i as integer,coldjunction as integer,adccount as integer, coldjunctionequiv as integer,temperature as integer
dim ktype(1090) as integer
dim testvoltage as float
'
INIT:
i2c open 400,1000
i=ktable() 'read in the therocouple lookup table
if i<>1 then end 'must be something wrong with the data table

'
MAIN:
testvoltage=0.02117 'k type voltage for just above 512 degrees from reference table
temperature=gettemp(0,DS18B20pin)
print "Temperature is " ,temperature," Degrees C"
testvoltage=-0.002857 'k type voltage for just below -78 degrees from reference table
temperature=gettemp(0,DS18B20pin)
print "Temperature is " ,temperature," Degrees C"
testvoltage=0 ' run the code for real
temperature=gettemp(0,DS18B20pin) 'ADC input pins shorted so should record cold junction temperature
print "Temperature is " ,temperature," Degrees C"

end
'

function gettemp(ADCchannel as integer, coldjunctionpin as integer)
if NOT testvoltage then
coldjunction=cint(ds18b20(coldjunctionpin))
coldjunctionequiv=ktype(coldjunction+zeroOffset)'get the number of ADC counts that the cold junction temperature would represent
' print "Coldjunction temperature is ",coldjunction," ADC equivalent is ",coldjunctionequiv
adccount=readadcraw16x8(ADCchannel) 'Measure thermocouple voltage with gain of 8 and 16 bits to give adequate resolution
else
coldjunctionequiv=0
adccount= cint(testvoltage/0.0000625*8)
print "Test ADC count = ",adccount
endif
adccount=adccount+coldjunctionequiv 'add in the cold junction temperature equivalent
temperature=findadc(adccount)
gettemp=temperature
end function
'
function findadc(adcnum as integer) 'just does a simple binary chop of the ADC count table to find the nearest entry
local top as integer, bottom as integer, work as integer, test as integer
top=1089
bottom=0 'set up search limits
if ktype(1089)<adcnum then
findadc=2000 'above range
exit function
endif
if ktype(0)>adcnum then
findadc=-2000 'below range
exit function
endif
do while top>bottom+1
work=(top+bottom)\2
test=ktype(work)
if test=adcnum then
findadc=work-zerooffset
end function
endif
if test> adcnum then
top=work
else
bottom=work
endif
loop
if (ktype(top)-adcnum)>=(adcnum-ktype(bottom)) then
findadc=bottom-zerooffset
else
findadc=top-zerooffset
endif
end function
'
function readadcraw16x8(channel as integer)
' config byte for chip is:
' bits 0 and 1 - Gain = 8
' bits 2 and 3 - # of bits = 16; 15 samples per second respectively
' bit 4 - 0=one-shot conversion ; we will always use 0 to allow changes to config e.g. which channel
' bits 5 and 6 - channel number 0-3
' bit 7 - set to start conversion, wait for clear to indicate conversion end
' max voltage for gain 8 = +/- 0.256V
local channelmask as integer,gainmask as integer, scratch as integer, timeout as integer
local configbyte as integer
local ADCret$ length 4
if channel<0 or channel>3 then
readadcraw16x8=100000000 'impossible value
exit function
endif
gainmask=3 'Gain of 8
timeout=ADCbits16timeout
configbyte=ADCbits16 or gainmask
channelmask=channel << 5
configbyte=configbyte or channelmask
i2c write ADCi2c, 0,1,configbyte
do
pause 5
i2c read ADCi2c, 0,4,ADCret$
scratch =asc(right$(ADCret$,1)) AND &B10000000
timeout=timeout-1
loop until (scratch=0) or (timeout=0)
if timeout <>0 then
readadcraw16x8=intconv(left$(ADCret$,2),signed)
else
readadcraw16x8=200000000 'impossible value
endif'
end function

'
function ktable
' This table gives the ADC counts at 16 bits resolution and gain of 8 for every temperature from -90 to 1000 degrees C
data 65121,65125,65129,65133,65137,65141,65146,65150,65154,65158, 65162,65166,65171,65175,65179,65183,65188,65192,65196,65201, 65205,65209,65214,65218,65222,65227,65231,65236,65240
data 65244,65249,65253,65258,65262,65267,65271,65276,65281,65285, 65290,65294,65299,65303,65308,65313,65317,65322,65326,65331, 65336,65341,65345,65350,65355,65359,65364,65369,65374
data 65378,65383,65388,65393,65398,65402,65407,65412,65417,65422, 65427,65432,65436,65441,65446,65451,65456,65461,65466,65471, 65476,65481,65486,65491,65496,65501,65506,65511,65516,65521, 65526,65531
data 0,5,10,15,20,25,30,35,41,46,51,56,61,66,71,76,82,87,92,97,10 2,107,113,118,123,128,133,138,144,149,154,159,164,170
data 175,180,185,191,196,201,206,212,217,222,227,233,238,243,248, 254,259,264,270,275,280,285,291,296,301,307,312,317,322,328, 333,338,344,349,354,360
data 365,370,376,381,386,392,397,402,408,413,418,423,429,434,439, 445,450,455,461,466,471,477,482,487,493,498,503,508,514,519, 524,530,535,540,546,551,556,561,567,572
data 577,582,588,593,598,604,609,614,619,625,630,635,640,646,651, 656,661,666,672,677,682,687,692,698,703,708,713,718,724,729, 734,739,744,750,755,760,765,770,775,781
data 786,791,796,801,806,811,817,822,827,832,837,842,847,852,858, 863,868,873,878,883,888,894,899,904,909,914,919,924,929,934, 940,945,950,955,960,965,970,975,980,985
data 991,996,1001,1006,1011,1016,1021,1026,1032,1037,1042,1047,10 52,1057,1062,1067,1072,1078,1083,1088,1093,1098,1103,1108,11 13,1119,1124,1129,1134,1139,1144,1149,1155,1160,1165,1170,11 75,1180,1186
data 1191,1196,1201,1206,1211,1217,1222,1227,1232
data 1237,1242,1248,1253,1258,1263,1268,1274,1279,1284,1289,1294
data 1300,1305,1310,1315,1320,1326,1331,1336,1341,1347,1352,1357, 1362,1368,1373,1378,1383,1389,1394,1399,1404,1410,1415,1420, 1425,1431,1436,1441,1446,1452,1457,1462,1468,1473,1478,1483, 1489,1494,1499,1504
data 1510,1515,1520,1526,1531,1536,1542,1547,1552,1557,1563,1568, 1573,1579,1584,1589,1594,1600,1605,1610,1616,1621,1626,1632, 1637,1642,1648,1653,1658,1664,1669,1674,1680,1685,1690,1696, 1701,1706,1712,1717
data 1722,1728,1733,1738,1744,1749,1754,1760,1765,1771,1776,1781, 1787,1792,1797,1803,1808,1813,1819,1824,1830,1835,1840,1846, 1851,1856,1862,1867,1873,1878,1883,1889,1894,1899,1905,1910, 1916,1921,1926,1932
data 1937,1942,1948,1953,1959,1964,1969,1975,1980,1985,1991,1996, 2002,2007,2012,2018,2023,2029,2034,2039,2045,2050,2056,2061, 2066,2072,2077,2083,2088,2093,2099,2104,2110,2115,2120,2126, 2131,2137,2142,2148
data 2153,2158,2164,2169,2175,2180,2185,2191,2196,2202,2207,2212, 2218,2223,2229,2234,2240,2245,2250,2256,2261,2267,2272,2278, 2283,2289,2294,2299,2305,2310,2316,2321,2327,2332,2337,2343, 2348,2354,2359,2365
data 2370,2375,2381,2386,2392,2397,2403,2408,2414,2419,2424,2430, 2435,2441,2446,2452,2457,2463,2468,2473,2479,2484,2490,2495, 2501,2506,2512,2517,2522,2528,2533,2539,2544,2550,2555,2561, 2566,2572,2577,2582
data 2588,2593,2599,2604,2610,2615,2621,2626,2632,2637,2642,2648, 2653,2659,2664,2670,2675,2681,2686,2692,2697,2702,2708,2713, 2719,2724,2730,2735,2741,2746,2752,2757,2762,2768,2774,2779, 2784,2790,2795,2801
data 2806,2812,2817,2823,2828,2834,2839,2844,2850,2855,2861,2866, 2872,2877,2883,2888,2894,2899,2904,2910,2915,2921,2926,2932, 2937,2943,2948,2954,2959,2964,2970,2975,2981,2986,2992,2997, 3003,3008,3014,3019
data 3025,3030,3035,3041,3046,3052,3057,3063,3068,3074,3079,3084, 3090,3095,3101,3106,3112,3117,3123,3128,3133,3139,3144,3150, 3155,3161,3166,3172,3177,3182,3188,3193,3199,3204,3210,3215, 3220,3226,3231,3237
data 3242,3248,3253,3259,3264,3270,3275,3280,3286,3291,3297,3302, 3308,3313,3318,3324,3329,3335,3340,3345,3351,3356,3362,3367, 3373,3378,3383,3389,3394,3400,3405,3410,3416,3421,3427,3432, 3438,3443,3448,3454
data 3459,3465,3470,3475,3481,3486,3492,3497,3502,3508,3513,3519, 3524,3529,3535,3540,3546,3551,3556,3562,3567,3573,3578,3583, 3589,3594,3599,3605,3610,3616,3621,3626,3632,3637,3643,3648, 3653,3659,3664,3670
data 3675,3680,3686,3691,3696,3702,3707,3712,3718,3723,3729,3734, 3739,3745,3750,3755,3761,3766,3771,3777,3782,3787,3793,3798, 3804,3809,3814,3820,3825,3830,3836,3841,3846,3852,3857,3862, 3868,3873,3878,3884
data 3889,3894,3900,3905,3910,3916,3921,3926,3932,3937,3942,3948, 3953,3958,3963,3969,3974,3979,3985,3990,3995,4001,4006,4011, 4017,4022,4027,4033,4038,4043,4048,4054,4059,4064,4070,4075, 4080,4085,4091,4096
data 4101,4106,4112,4117,4122,4128,4133,4138,4143,4149,4154,4159, 4165,4170,4175,4180,4186,4191,4196,4201,4207,4212,4217,4222, 4228,4233,4238,4243,4249,4254,4259,4264,4270,4275,4280,4285, 4291,4296,4301,4306
data 4312,4317,4322,4327,4333,4338,4343,4348,4354,4359,4364,4369, 4374,4380,4385,4390,4395,4401,4406,4411,4416,4421,4426,4432, 4437,4442,4447,4453,4458,4463,4468,4473,4479,4484,4489,4494, 4499,4505,4510,4515
data 4520,4525,4530,4536,4541,4546,4551,4556,4562,4567,4572,4577, 4582,4587,4593,4598,4603,4608,4613,4618,4623,4629,4634,4639, 4644,4649,4654,4660,4665,4670,4675,4680,4685,4690,4696,4701, 4706,4711,4716,4721
data 4726,4732,4737,4742,4747,4752,4757,4762,4767,4773,4778,4783, 4788,4793,4798,4803,4808,4814,4819,4824,4829,4834,4839,4844, 4849,4854,4860,4865,4870,4875,4880,4885,4890,4895,4900,4905, 4910,4915,4921,4926
data 4931,4936,4941,4946,4951,4956,4961,4966,4971,4976,4982,4987, 4992,4997,5002,5007,5012,5017,5022,5027,5032,5037,5042,5047, 5052,5057,5062,5068,5073,5078,5083,5088,5093,5098,5103,5108, 5113,5118,5123,5128
data 5133,5138,5143,5148,5153,5158,5163,5168,5173,5178,5183,5188, 5193,5198,5203,5208,5213,5218,5223,5228,5233,5238,5243,5248, 5253,5258,5263,5268,5273,5278
Local i,j
j=-420 ' 5 less than lowest value in the table
ktable=1
for i= 0 to 1089
read ktype(i)
if ktype(i)>32767 then ktype(i)=ktype(i)-65536
if (ktype(i)-j) <4 or (ktype(i)-j) >7 then ktable=0 'check no errors in table
j=ktype(i)
next i
end function

CFunction intconv 'convert data read from i2c to integer including extending sign bit across the 64 bit integer
00000000
27bdfff8 00001021 00001821 afa20000 afa30004 90880000 1900000b 01003821
2503ffff 03a31821 24020001 00823021 90c60000 a0660000 24420001 00e2302a
10c0fffa 2463ffff 8ca20000 1040000d 03a81021 9042ffff 30420080 10400009
29020008 10400007 03a81021 27a40008 2403ffff a0430000 24420001 5444fffe
a0430000 8fa20000 8fa30004 03e00008 27bd0008
End CFunction