How can I upload and plot temperature values that are both above zero (e.g., ambient) and below zero (e.g., in a freezer)?
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I wish to upload and plot on channel chart both positive and negative temperatures from DS18B20 sensor. While I can see the positive temperatures properly on the chart, the negative temperatures also show as above zero. The code snippet is as below:
if(temp_data & 0x80)
{
temp_data = (~temp_data)+1;
sprintf(esp_buff, "GET /update?api_key=%s&field1=%d", API_WRITE_KEY, -temp_data);
}
else
{
sprintf(esp_buff, "GET /update?api_key=%s&field1=%d", API_WRITE_KEY, temp_data);
}
//sprintf(esp_buff, "GET /update?api_key=%s&field1=%d", API_WRITE_KEY, temp_data);
ESP8266_Send(esp_buff);
It can be seen that the last two readings which are -6 and -9 deg C,show as +6 and +9 deg C. what should I do to make them come below the zero line?
5 Comments
dpb
on 12 Sep 2022
I backed out of the thread because I have no Arduino experience nor one at hand to play with to learn about, but the poking around I did indicated there are at least a couple of libraries that can be used to interact with the one-wire device...it appeared with those one just reads a buffer and magic happens...
Answers (3)
Image Analyst
on 12 Sep 2022
If you can get your data into a double image, you can use
imshow(yourTemperatureImage, []);
0 Comments
Christopher Stapels
on 12 Sep 2022
Edited: Christopher Stapels
on 12 Sep 2022
I think the library answer seems best.
This article seems to indicate that you can use arduino libraries in Atmel Studio.
If you wanted to fix the code above, I would start by writing rawtemp to thingspeak and seeing if the negative values are encoded in there. Then you can fix your code to translate rawtemp appropriately.
sprintf(esp_buff, "GET /update?api_key=%s&field1=%d&field2=%d", API_WRITE_KEY, temp_data,rawtemp);
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