DS1620 SMT version - different values?

[Build-A-Burger]

I bought some DS1620's in the SMT version and I run the same code that works fine for the dip version and I get different values.
The data sheet says:
Measures temperatures from -55°C to +125°C
in 0.5°C increments; Fahrenheit equivalent is
-67°F to +257°F in 0.9°F increments

TEMPERATURE/DATA RELATIONSHIPS Table 1

TEMP	DIGITAL OUTPUT (Binary)	DIGITAL OUTPUT (Hex)
+125°C	0 11111010	00FA
+25°C	0 00110010	0032h
+½°C	0 00000001	0001h
+0°C	0 00000000	0000h
-½°C	1 11111111	01FFh
-25°C	1 11001110	01CEh
-55°C	1 10010010	0192h

I use a lookup table:

typedef struct
{
    char str[10];
    int raw;
}RAW_DATA;

static RAW_DATA raw_data[360] =
{{"31.1\0", 511},
{"30.2\0", 510},
{"29.3\0", 509},
{"28.4\0", 508},
{"27.5\0", 507},
{"26.6\0", 506},
{"25.7\0", 505},
{"24.8\0", 504},
{"23.9\0", 503},
{"23.0\0", 502},
{"22.1\0", 501},
{"21.2\0", 500},
{"20.3\0", 499},
{"19.4\0", 498},
{"18.5\0", 497},
{"17.6\0", 496},
{"16.7\0", 495},
{"15.8\0", 494},
{"14.9\0", 493},
{"14.0\0", 492},
{"13.1\0", 491},
{"12.2\0", 490},
{"11.3\0", 489},
{"10.4\0", 488},
{"9.5\0", 487},
{"8.6\0", 486},
{"7.7\0", 485},
{"6.8\0", 484},
{"5.9\0", 483},
{"5.0\0", 482},
{"4.1\0", 481},
{"3.2\0", 480},
{"2.3\0", 479},
{"1.4\0", 478},
{"0.5\0", 477},
{"-0.4\0", 476},
{"-1.3\0", 475},
{"-2.2\0", 474},
{"-3.1\0", 473},
{"-4.0\0", 472},
{"-4.9\0", 471},
{"-5.8\0", 470},
{"-6.7\0", 469},
{"-7.6\0", 468},
{"-8.5\0", 467},
{"-9.4\0", 466},
{"-10.3\0", 465},
{"-11.2\0", 464},
{"-12.1\0", 463},
{"-13.0\0", 462},
{"-13.9\0", 461},
{"-14.8\0", 460},
{"-15.7\0", 459},
{"-16.6\0", 458},
{"-17.5\0", 457},
{"-18.4\0", 456},
{"-19.3\0", 455},
{"-20.2\0", 454},
{"-21.1\0", 453},
{"-22.0\0", 452},
{"-22.9\0", 451},
{"-23.8\0", 450},
{"-24.7\0", 449},
{"-25.6\0", 448},
{"-26.5\0", 447},
{"-27.4\0", 446},
{"-28.3\0", 445},
{"-29.2\0", 444},
{"-30.1\0", 443},
{"-31.0\0", 442},
{"-31.9\0", 441},
{"-32.8\0", 440},
{"-33.7\0", 439},
{"-34.6\0", 438},
{"-35.5\0", 437},
{"-36.4\0", 436},
{"-37.3\0", 435},
{"-38.2\0", 434},
{"-39.1\0", 433},
{"-40.0\0", 432},
{"-40.9\0", 431},
{"-41.8\0", 430},
{"-42.7\0", 429},
{"-43.6\0", 428},
{"-44.5\0", 427},
{"-45.4\0", 426},
{"-46.3\0", 425},
{"-47.2\0", 424},
{"-48.1\0", 423},
{"-49.0\0", 422},
{"-49.9\0", 421},
{"-50.8\0", 420},
{"-51.7\0", 419},
{"-52.6\0", 418},
{"-53.5\0", 417},
{"-54.4\0", 416},
{"-55.3\0", 415},
{"-56.2\0", 414},
{"-57.1\0", 413},
{"-58.0\0", 412},
{"-58.9\0", 411},
{"-59.8\0", 410},
{"-60.7\0", 409},
{"-61.6\0", 408},
{"-62.5\0", 407},
{"-63.4\0", 406},
{"-64.3\0", 405},
{"-65.2\0", 404},
{"-66.1\0", 403},
{"257.0\0", 250},
{"256.1\0", 249},
{"255.2\0", 248},
{"254.3\0", 247},
{"253.4\0", 246},
{"252.5\0", 245},
{"251.6\0", 244},
{"250.7\0", 243},
{"249.8\0", 242},
{"248.9\0", 241},
{"248.0\0", 240},
{"247.1\0", 239},
{"246.2\0", 238},
{"245.3\0", 237},
{"244.4\0", 236},
{"243.5\0", 235},
{"242.6\0", 234},
{"241.7\0", 233},
{"240.8\0", 232},
{"239.9\0", 231},
{"239.0\0", 230},
{"238.1\0", 229},
{"237.2\0", 228},
{"236.3\0", 227},
{"235.4\0", 226},
{"234.5\0", 225},
{"233.6\0", 224},
{"232.7\0", 223},
{"231.8\0", 222},
{"230.9\0", 221},
{"230.0\0", 220},
{"229.1\0", 219},
{"228.2\0", 218},
{"227.3\0", 217},
{"226.4\0", 216},
{"225.5\0", 215},
{"224.6\0", 214},
{"223.7\0", 213},
{"222.8\0", 212},
{"221.9\0", 211},
{"221.0\0", 210},
{"220.1\0", 209},
{"219.2\0", 208},
{"218.3\0", 207},
{"217.4\0", 206},
{"216.5\0", 205},
{"215.6\0", 204},
{"214.7\0", 203},
{"213.8\0", 202},
{"212.9\0", 201},
{"212.0\0", 200},
{"211.1\0", 199},
{"210.2\0", 198},
{"209.3\0", 197},
{"208.4\0", 196},
{"207.5\0", 195},
{"206.6\0", 194},
{"205.7\0", 193},
{"204.8\0", 192},
{"203.9\0", 191},
{"203.0\0", 190},
{"202.1\0", 189},
{"201.2\0", 188},
{"200.3\0", 187},
{"199.4\0", 186},
{"198.5\0", 185},
{"197.6\0", 184},
{"196.7\0", 183},
{"195.8\0", 182},
{"194.9\0", 181},
{"194.0\0", 180},
{"193.1\0", 179},
{"192.2\0", 178},
{"191.3\0", 177},
{"190.4\0", 176},
{"189.5\0", 175},
{"188.6\0", 174},
{"187.7\0", 173},
{"186.8\0", 172},
{"185.9\0", 171},
{"185.0\0", 170},
{"184.1\0", 169},
{"183.2\0", 168},
{"182.3\0", 167},
{"181.4\0", 166},
{"180.5\0", 165},
{"179.6\0", 164},
{"178.7\0", 163},
{"177.8\0", 162},
{"176.9\0", 161},
{"176.0\0", 160},
{"175.1\0", 159},
{"174.2\0", 158},
{"173.3\0", 157},
{"172.4\0", 156},
{"171.5\0", 155},
{"170.6\0", 154},
{"169.7\0", 153},
{"168.8\0", 152},
{"167.9\0", 151},
{"167.0\0", 150},
{"166.1\0", 149},
{"165.2\0", 148},
{"164.3\0", 147},
{"163.4\0", 146},
{"162.5\0", 145},
{"161.6\0", 144},
{"160.7\0", 143},
{"159.8\0", 142},
{"158.9\0", 141},
{"158.0\0", 140},
{"157.1\0", 139},
{"156.2\0", 138},
{"155.3\0", 137},
{"154.4\0", 136},
{"153.5\0", 135},
{"152.6\0", 134},
{"151.7\0", 133},
{"150.8\0", 132},
{"149.9\0", 131},
{"149.0\0", 130},
{"148.1\0", 129},
{"147.2\0", 128},
{"146.3\0", 127},
{"145.4\0", 126},
{"144.5\0", 125},
{"143.6\0", 124},
{"142.7\0", 123},
{"141.8\0", 122},
{"140.9\0", 121},
{"140.0\0", 120},
{"139.1\0", 119},
{"138.2\0", 118},
{"137.3\0", 117},
{"136.4\0", 116},
{"135.5\0", 115},
{"134.6\0", 114},
{"133.7\0", 113},
{"132.8\0", 112},
{"131.9\0", 111},
{"131.0\0", 110},
{"130.1\0", 109},
{"129.2\0", 108},
{"128.3\0", 107},
{"127.4\0", 106},
{"126.5\0", 105},
{"125.6\0", 104},
{"124.7\0", 103},
{"123.8\0", 102},
{"122.9\0", 101},
{"122.0\0", 100},
{"121.1\0", 99},
{"120.2\0", 98},
{"119.3\0", 97},
{"118.4\0", 96},
{"117.5\0", 95},
{"116.6\0", 94},
{"115.7\0", 93},
{"114.8\0", 92},
{"113.9\0", 91},
{"113.0\0", 90},
{"112.1\0", 89},
{"111.2\0", 88},
{"110.3\0", 87},
{"109.4\0", 86},
{"108.5\0", 85},
{"107.6\0", 84},
{"106.7\0", 83},
{"105.8\0", 82},
{"104.9\0", 81},
{"104.0\0", 80},
{"103.1\0", 79},
{"102.2\0", 78},
{"101.3\0", 77},
{"100.4\0", 76},
{"99.5\0", 75},
{"98.6\0", 74},
{"97.7\0", 73},
{"96.8\0", 72},
{"95.9\0", 71},
{"95.0\0", 70},
{"94.1\0", 69},
{"93.2\0", 68},
{"92.3\0", 67},
{"91.4\0", 66},
{"90.5\0", 65},
{"89.6\0", 64},
{"88.7\0", 63},
{"87.8\0", 62},
{"86.9\0", 61},
{"86.0\0", 60},
{"85.1\0", 59},
{"84.2\0", 58},
{"83.3\0", 57},
{"82.4\0", 56},
{"81.5\0", 55},
{"80.6\0", 54},
{"79.7\0", 53},
{"78.8\0", 52},
{"77.9\0", 51},
{"77.0\0", 50},
{"76.1\0", 49},
{"75.2\0", 48},
{"74.3\0", 47},
{"73.4\0", 46},
{"72.5\0", 45},
{"71.6\0", 44},
{"70.7\0", 43},
{"69.8\0", 42},
{"68.9\0", 41},
{"68.0\0", 40},
{"67.1\0", 39},
{"66.2\0", 38},
{"65.3\0", 37},
{"64.4\0", 36},
{"63.5\0", 35},
{"62.6\0", 34},
{"61.7\0", 33},
{"60.8\0", 32},
{"59.9\0", 31},
{"59.0\0", 30},
{"58.1\0", 29},
{"57.2\0", 28},
{"56.3\0", 27},
{"55.4\0", 26},
{"54.5\0", 25},
{"53.6\0", 24},
{"52.7\0", 23},
{"51.8\0", 22},
{"50.9\0", 21},
{"50.0\0", 20},
{"49.1\0", 19},
{"48.2\0", 18},
{"47.3\0", 17},
{"46.4\0", 16},
{"45.5\0", 15},
{"44.6\0", 14},
{"43.7\0", 13},
{"42.8\0", 12},
{"41.9\0", 11},
{"41.0\0", 10},
{"40.1\0", 9},
{"39.2\0", 8},
{"38.3\0", 7},
{"37.4\0", 6},
{"36.5\0", 5},
{"35.6\0", 4},
{"34.7\0", 3},
{"33.8\0", 2},
{"32.9\0", 1},
{"32  \0", 0}};

What should be around 50F comes back as a raw value of 452. I put the sensor in an ice bath and got a raw value of 421. Is the SMT version different somehow?

 

[KlausST]

Hi,

If I encounter any software problem, then I first try to exclude any "additional" software.
Thus in your case if you want to check sensor data, I'd exclude the fahrenheit conversion.
Ceslsius is rather straight forward: 0°C in icewater, linearely rising to 100°C with boiling water.
So it's rather easy to check.

If I want to check the conversion ... then I'd exclude the sensor communication.
Just using an online celsius to fahrenheit calculator
I expected your "uncommented" snippet of code to be a fahrenheit to celsius conversion. This seems not to be the case.

I didn't go deeper, because I generally don't spend time on uncommented code. It just leads to assumptions, guessing, misunderstanding...

My recommendation: If you want someone to spend time with your code:
* first spend your time to comment the code
* post the whole code

Also we don't see how you debug the problem. Like how you get the "raw values" of 452 and 421. Display? UART? What code?

Klaus

 

[betwixt]

Why even use a look-up table when the result is "(value * 1.8 ) + 32" ? I have some doubts about the accuracy of that table. The C to F conversion looks suspicious.

I agree with Klaus though, a list of numbers tells us nothing if we don't know how you reference them.

Brian.

 

[Build-A-Burger]

If I wanted to convert to C:

if(val >= 0 && val <= 250)
{
C = val/2;

}
else if(val >= 403 && val <= 511)
{
C = (val - 512)/2;
}

when the temp drops below 32F then the values returned have an offset of 511.
The outside temps here dropped below 32F overnight and I could see the raw values returned from the other sensors that used the dip version cross over from 0 to 511 down to 508 which is 23.4F.

The one with the SMT is inside so I'll have to put it outside or next to one of the dip versions and use an ice bath to see them both side by side. I checked some of the values in the lookup table with the above formula and did the C to F conversions, so the lookup table is correct. I could upload the actual code I use, but it's the same for both. I was just thinking the values returned by the SMT version were shifted or off by a factor. I tried clearing the MSB and bit reversing it to try and see a pattern.

source code

 

[Build-A-Burger]

I think I need a 1k resistor in series with the DQ and then I need some kind of RC ckt on the VDD. I saw a diagram somewhere. Let me take care of that first and then try it again.

 

[D.A.(Tony)Stewart]

After you confirm valid raw data,try this

#include <stdio.h>

typedef struct
{
int temp;
int digital_output;
} TEMP_DIGITAL_OUTPUT;

// Define the input values
TEMP_DIGITAL_OUTPUT input_data[] = {
{125, 0x00FA},
{25, 0x0032},
{0.5, 0x0001},
{0, 0x0000},
{-0.5, 0x01FF},
{-25, 0x01CE},
{-55, 0x0192}
};

int main()
{
int i, count;
float sum_temp = 0;

// Calculate the average temperature
count = sizeof(input_data) / sizeof(input_data[0]);
for (i = 0; i < count; i++) {
if (input_data.digital_output & 0x8000) { // Check if the temperature is negative
input_data.temp = -(~(input_data.digital_output - 1) & 0x7FFF); // Convert the two's complement
} else {
input_data.temp = input_data.digital_output & 0x7FFF; // Positive temperature
}
sum_temp += input_data.temp;
}
float average_temp = sum_temp / count;

// Print the results
printf("Input values:\n");
for (i = 0; i < count; i++) {
printf("%d°C 0x%04Xh\n", input_data.temp, input_data.digital_output);
}
printf("\nAverage temperature: %.2f°C\n", average_temp);

return 0;
}