| Author |
Message |
|
|
 Posted: Jun 07, 2012 - 10:11 PM |
|
Joined: Jun 07, 2012
Posts: 5
|
|
Hi everyone!
I need help with interfacing MAX6675 using SPI on ATMEGA16 - in GCC!!!
I have got K-type thermocouple (inside soldering pen) and i would like to get it's temperature in Celsius.
I was browsing the net for some tutorials or examples but nothing worked so i crated this topic.
I found some libraries too, but most of them was for arduino or they were too complicated.
I have learned basics about SPI and I2C, it's difficult to create library like this for me.
I'm newbie using MCUs.
Thank you all for helping me. |
Last edited by fukanlubos on Jun 11, 2012 - 07:53 AM; edited 1 time in total
|
| |
|
|
|
|
|
|
Posted: Jun 07, 2012 - 10:31 PM |
|
Joined: Nov 22, 2002
Posts: 12049
Location: Tangent, OR, USA
|
|
You do not need a library. There are code examples of SPI use in the Mega16 spec sheet. SPI is so fast that you generally don't even need interrupts. And, this is really not a "gcc problem"; its pretty much the same for all c compilers.
Jim |
_________________
Jim Wagner
Oregon Research Electronics, Consulting Div.
Tangent, OR, USA
"The only thing standing between us and victory is defeat" P.G.Wodhouse in Wooster & Jeeves series
|
| |
|
|
|
|
|
|
Posted: Jun 07, 2012 - 10:47 PM |
|
Joined: Jun 07, 2012
Posts: 5
|
|
| Thank you Jim, I will try to find it out. |
_________________
Luboš Fukan
AVR newbie, Czech Republic
|
| |
|
|
|
|
|
|
Posted: Jun 07, 2012 - 11:41 PM |
|
Joined: Nov 22, 2002
Posts: 12049
Location: Tangent, OR, USA
|
|
That one is specially easy. No registers to write to. Just read.
SO pin connects to the AVR MISO pin
SCK pin connects to the AVR SCK pin
/CS pin connects to the /SS pin
The one non-intuitive thing you have to do with the master (the AVR) is that IT has to "transmit" some byte for every byte it receives. So, you write anything to the data register, start it, wait for it to finish, then read the data register. Makes no difference what you transmit because it does not go anywhere.
You also have to manage the /SS pin in software. Note the section /SS Pin Functionality for details.
Jim |
_________________
Jim Wagner
Oregon Research Electronics, Consulting Div.
Tangent, OR, USA
"The only thing standing between us and victory is defeat" P.G.Wodhouse in Wooster & Jeeves series
|
| |
|
|
|
|
|
|
Posted: Jun 08, 2012 - 04:44 PM |
|
Joined: Jun 07, 2012
Posts: 5
|
|
Hi, I have read atmega16 and max6675 datasheets and atmel spi guide too. I made the following code: http://pastebin.com/aKk58z36
While termocouple is connected, program cant pass trought sending spi so the display shows only max6675 test.
When i diconnect termocouple from max6675 or whole max6675 and restart the program it says that termocouple is not connected. Haven't you any advice what can be wrong?
Thank you very much!
Luboš Fukan |
|
|
| |
|
|
|
|
|
|
Posted: Jun 10, 2012 - 10:18 PM |
|
Joined: Nov 28, 2004
Posts: 3552
Location: San Diego, Ca
|
|
Luboš, put up a schematic. The OP will be moved to the GE forum, o you ought to edit your title and put thermocouple in it too.
You ought to code without the "magic number" thing. Better to do, for example:
Code:
#define MAX6675_CS 0
void max6675_select() {
cbi(PORTB, 4);
PORTA &= ~( 1<< MAX6675_CS ); //led diode indication instead of debugger :((
}
Much better for getting what code doing ! You're not initializing SPI completely,get AVR151 from Atmel page. Move the spi_init() code out of the read() function and make it have own function ( why do init() every time read() called ?  ) . |
_________________
1) Studio 4.18 build 716 (SP3)
2) WinAvr 20100110
3) PN, all on Doze XP... For Now
A) Avr Dragon ver. 1
B) Avr MKII ISP, 2009 model
C) MKII JTAGICE ver. 1
Last edited by indianajones11 on Jun 23, 2012 - 01:11 PM; edited 1 time in total
|
| |
|
|
|
|
|
|
Posted: Jun 10, 2012 - 11:31 PM |
|
Joined: Sep 04, 2002
Posts: 21261
Location: Orlando Florida
|
|
|
Code:
#define CSLO() PORTC &= ~0x01
#define CSHI() PORTC |= 0x01
#define C1LO() PORTC &= ~0x02
#define C1HI() PORTC |= 0x02
unsigned int raw; //raw bits from max6675 (1/16th degrees)
float fqdeg,fqdegsm;
//----------------------------
void readmax6675(void){
//read max6675 thermocouple preamp takes 220ms!
unsigned int dh,dl;
unsigned int qdeg; //quarter degrees
INTR_OFF();
SPCR=0x5B; //0x5b =0x53 | 0x08 slow spi, clk pol flipped for max6675
CSLO(); //conv halt, output bit 0
spiout8(0); //send dummy byte
dh=readspi(); //read hi byte
spiout8(0); //send dummy byte
dl=readspi(); //read lo byte
CSHI(); //conv resume
SPCR=0x50; //fastest spi back on for needle
INTR_ON();
raw=dh*256 + dl; //raw thermocouple reading 1/16th deg C
qdeg=raw >> 2; //12 bit unsigned integer number (quarter degrees C)
fqdeg=qdeg;
fqdegsm += 0.1*(fqdeg-fqdegsm);
degC=fqdegsm*0.25;
degF=degC*1.8 + 32.0;
}
|
_________________
Imagecraft compiler user
|
| |
|
|
|
|
|
|
Posted: Jun 11, 2012 - 02:07 PM |
|
Joined: Jun 07, 2012
Posts: 5
|
|
| Thank you guys i will try it all tomorrow, now i must learn to school. |
_________________
Luboš Fukan
AVR newbie, Czech Republic
|
| |
|
|
|
|
|
|
Posted: Jun 12, 2012 - 09:12 PM |
|
Joined: Apr 25, 2004
Posts: 3809
Location: Denmark
|
|
|
indianajones11 wrote:
* ( that letter key on my keyboard not working )
*PI completely,
Is that a new american virus (eating kbd S'es ??)
You're the 2'nd i have seen today.
/Bingo |
|
|
| |
|
|
|
|
|
|
Posted: Jun 23, 2012 - 01:13 PM |
|
Joined: Nov 28, 2004
Posts: 3552
Location: San Diego, Ca
|
|
| Bingo, for me I got lucky since it started working again. Probably a stuck key . |
_________________
1) Studio 4.18 build 716 (SP3)
2) WinAvr 20100110
3) PN, all on Doze XP... For Now
A) Avr Dragon ver. 1
B) Avr MKII ISP, 2009 model
C) MKII JTAGICE ver. 1
|
| |
|
|
|
|
|
|
Posted: Sep 09, 2012 - 05:13 PM |
|
Joined: Jun 07, 2012
Posts: 5
|
|
So it took me a while to realize that the mcu is broken. I soleved it another way, i have used amplifier for the thermocouple output, i calibrated it and i read its value using adc (1°C=10mV) and woho it works. So thank you all. spi works great with another mcu.  |
_________________
Luboš Fukan
AVR newbie, Czech Republic
|
| |
|
|
|
|
|
|
Posted: Sep 10, 2012 - 05:51 AM |
|
Joined: Nov 28, 2004
Posts: 3552
Location: San Diego, Ca
|
|
| Very good job, way to stick with it ! |
_________________
1) Studio 4.18 build 716 (SP3)
2) WinAvr 20100110
3) PN, all on Doze XP... For Now
A) Avr Dragon ver. 1
B) Avr MKII ISP, 2009 model
C) MKII JTAGICE ver. 1
|
| |
|
|
|
|
|
FAQ
Search
Register
Log in to check your private messages
Log in
Maximize
RSS
