Having trouble with SERIN command and MAX6675

[emerson]

Normally black boxes are a contrast problem, but is the LCD cod is the same as on another project...

Post your whole current code and config setup so we can have a look.

This is what I have so far:

 INCLUDE "modedefs.bas"

define    OSC 4

'Alias pins - MAX6675 temp sensor
MXSCLK  var     PORTA.5   'Clock
MXCS     var     PORTA.2    'Chip Select
MXSO     Var     PORTA.4   'Serial out

 'Allocate MAX6875 Variables
MXTemp   var     word    'raw data from 6675/type K sensor
TempC   var     word    'converted to degrees C


'-----------Read and display temperature from MAX6675-----------
MXCS = 0  'Chip select low
shiftin MXSO, MXSCLK, 0, [MXTemp\16]   'read the data to MXTemp
MXCS = 1    'Chip select high
TempC = MXtemp >> 5   'right shift the data 5 places to get degrees C (Read the Data sheet)
LCDOUT $fe,2,"Temp = ", DEC TempC, "degrees C "  ' Spit it out on an LCD

The contrast on the LCD is alright I have it adjusted properly. What does "Invalid RAM location specified" mean?

[mackrackit]

What does "Invalid RAM location specified" mean?

In this case it means you are compiling a LCDOUT command without having LCD defines.

[emerson]

In this case it means you are compiling a LCDOUT command without having LCD defines.

Alright, I put my LCD defines into the code and i get a readout of 32 degrees F (the temp probe on my multimeter reads the room is 70 degrees F), but the temperature didn't change when I put a lighter to the temp probe. I added a main loop to cycle through the program but that didn't help. Is it something with the SHIFTIN command or could I have fried the surface mount chip when soldering leads to it?
And thank you for your help. I've been working on this for weeks with no turnout.

Here is my current code:

INCLUDE "modedefs.bas"

define    OSC 4

'Define LCD registers and bits
DEFINE LCD_DREG PORTC 'Define PIC port used for LCD Data lines
DEFINE LCD_DBIT 0 'LCD Data Starting Bit = Bit 0 or 4
DEFINE LCD_EREG PORTC 'Define PIC port used for E line of LCD
DEFINE LCD_EBIT 5 'Define Port pin used for E connection
DEFINE LCD_RSREG PORTC 'Define PIC port used for RS line of LCD
DEFINE LCD_RSBIT 4 'Define Port pin used for RS connection
DEFINE LCD_BITS 4 'Define the 4 bit communication mode to LCD
DEFINE LCD_LINES 2 'Define using a 2 line LCD
DEFINE LCD_COMMANDUS 2000 'Define delay time between sending LCD commands
DEFINE LCD_DATAUS 50 'Define delay time between data sent.

Pause 500 ' Wait for LCD to startup

'Alias pins - MAX6675 temp sensor
MXSCLK  var     PORTA.5   'Clock MAX pin 5
MXCS     var     PORTA.2    'Chip Select MAX pin 6
MXSO     Var     PORTA.4   'Serial out MAX pin 7

 'Allocate MAX6875 Variables
MXTemp   var     word    'raw data from 6675/type K sensor
TempC   var     word    'converted to degrees C
TempF     var   word


'-----------Read and display temperature from MAX6675-----------

Main:

MXCS = 0  'Chip select low
shiftin MXSO, MXSCLK, 0, [MXTemp\16]   'read the data to MXTemp
MXCS = 1    'Chip select high
TempC = MXtemp >> 5   'right shift the data 5 places to get degrees C (Read the Data sheet)
TempF = ABS(TempC) */ 461
TempF = TempF + 32
lcdout $fe, 1
LCDOUT $fe,2,"  Temperature "
lcdout $fe, $c0, " Faren=", DEC Tempf, " Cel=", dec tempc ' Spit it out on an LCD
pause 500

goto main

[Bruce]

You want to read each bit on the falling edge of the clock so use mode 2. And you only need to shift MXtemp >> 3. Not 5.

[emerson]

You want to read each bit on the falling edge of the clock so use mode 2. And you only need to shift MXtemp >> 3. Not 5.

I changed both but there's still no response? On the datasheet it says the MAX6675 serial clock frequency is 4.3MHz, and I'm running my pic at 4MHz, will this effect data communication?

[Bruce]

If you have an O-scope check the data out pin. That will at least let you know if it's responding.

[emerson]

If you have an O-scope check the data out pin. That will at least let you know if it's responding.

the O-scope test checked out alright