max6675

temtronic · Posted: Sat Dec 09, 2017 6:39 am

You have to 'split up' your program and send data to a PC terminal program.

You need to be able to see
1) the raw data from TC device
2) the result of the sortout() function
3) the result of the toCalcTC() function
When you do this ,you'll be able to see the result of each operation you're asking the PIC to do, Right now there is no way to see if the TC device is actually returning the correct data or if one of the 'math' functions is really causing the problem. Often 'casting' or 'math' will cause problems.

If you can't send to PC, then instead of reading the TC device, use a known number as the data and see what happens. For test purposes I'd try 5 values that cover the range of the TC device.IE if the range was from 0 to 100, I'd use 0, 25,50,80,100. Now if the LED display shows the correct result for the values you use as being 'TC device data', then you know the 'math' functions are correct. Therefore the bad data must be the TC device data. If that's the case you could have 1) incorrect wiring, 2) wrong SPI mode( it's 0 according to earlier posts) 3 defective chip 4) bad sensor or something else.

While the 3 digit LED display is fine for the final product, for 'debug' purpose you really need to send the data to a PC, an LCD module or even 16 LEDs.

Also, I'd put the 'LED display code' inside a 'function', like you did the 'math' routines. Since it does work it will make the main() code simpler to look at. something like void dspLED_TC_data(int16 result). I like names that say what they do, easier for me.

Ttelmah · Joined: 11 Mar 2010 Posts: 19619

Ttelmah · Joined: 11 Mar 2010 Posts: 19619

Er.

According to the picture of the module, it has the pins as GND, VCC, CLX, CS, DATA.

You post:
16f72 max6675 module

14 3
16 5
17 4
vcc 2
gnd 1

Now pin 14 is C3, 16 is C5, and 17 is C6. Disagrees totally with the pins you are using in the setup. No wonder it doesn't work.

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Ttelmah, I get his connections as follows and it looks OK to me.

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

madhusuthanan · Joined: 23 Aug 2017 Posts: 15

I find the solution for that issue not it is showing the correct value. I made manually get the value of the module with software spi communication. manually calculated from spi communication. thanks for guidance for finding the issue.