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autova
Joined: 24 May 2011
Posts: 14
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| weird reading on hmc6352 |
 Posted: Tue May 24, 2011 10:13 am |
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I'm using pcm programmer coding to test hmc6352 with pic16f877a to read value from that compass. Reading I get from that compass are this
"|xxxp@@@@```|``p@ppp|||@`@@@@@@@@"
what is the problem ? can anyone help me ?
this the code
| Code: |
#include <16F877A.H>
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
#use i2c(Master, sda=PIN_C4, scl=PIN_C3, FORCE_HW)
#define HMC6352_I2C_WRITE_ADDRESS 0x42
#define HMC6352_I2C_READ_ADDRESS 0x43
#define HMC6352_GET_DATA_COMMAND 0x41
// Read the compass heading. This is in units
// of 1/10's of a degree, from 0 to 3599.
int16 HMC6352_read_heading(void)
{
int8 lsb;
int8 msb;
i2c_start();
i2c_write(HMC6352_I2C_WRITE_ADDRESS);
i2c_write(HMC6352_GET_DATA_COMMAND);
i2c_stop();
delay_ms(7); // Allow 1 ms extra for safety
i2c_start();
i2c_write(HMC6352_I2C_READ_ADDRESS);
msb = i2c_read();
lsb = i2c_read(0);
i2c_stop();
return((int16)lsb | ((int16)msb << 8));
}
//===================================
void main()
{
int16 heading;
while(1)
{
heading = HMC6352_read_heading();
printf("Heading in degrees = %lu\n\r", heading/10);
delay_ms(1000);
}
}
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help me anyone |
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temtronic
Joined: 01 Jul 2010
Posts: 9226
Location: Greensville,Ontario
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| Posted: Tue May 24, 2011 11:04 am |
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| What value of pullups do you have of the I2C lines ? |
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dyeatman
Joined: 06 Sep 2003
Posts: 1934
Location: Norman, OK
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| Posted: Tue May 24, 2011 11:29 am |
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Where and how are you getting this? Is your example what you get from the
Printf statement on your PC? If it is, and all you get is garbage, you have an
RS232 problem you must solve first and forget about the sensor until it is fixed...
If the RS232 was OK you should at least see: | Code: | | Heading in degrees = |
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autova
Joined: 24 May 2011
Posts: 14
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| Posted: Tue May 24, 2011 1:44 pm |
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temtronic = what value of pullups did you mean ? i dont understan
dyeatman = i get from this forum also
http://www.ccsinfo.com/forum/viewtopic.php?t=45123&view=previous
my rs232 is ok because it can display statement but when i program this code , it show that result and nothing happen . |
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dyeatman
Joined: 06 Sep 2003
Posts: 1934
Location: Norman, OK
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| Posted: Tue May 24, 2011 1:48 pm |
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OK, to be clear, when you run the program it displays the line "Heading in degrees =" on your PC followed by garbage correct?
If that's the case then you need to verify the parameter values being passed
from the int16 HMC6352_read_heading(void) subroutine. The best way to do
this is to assign values to lsb and msb right after the I2C-stop statement to see if they get passed correctly out of the subroutine.
I could outright give you the answer but you can benefit from the
troubleshooting if I help you figure it out.
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Last edited by dyeatman on Tue May 24, 2011 1:57 pm; edited 1 time in total |
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autova
Joined: 24 May 2011
Posts: 14
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| Posted: Tue May 24, 2011 1:54 pm |
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| dyeatman = the problems is the line "heading in degree" not there . seriously , i have don't know what to do right . give me some hint where i can settle this thing ? please |
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dyeatman
Joined: 06 Sep 2003
Posts: 1934
Location: Norman, OK
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| Posted: Tue May 24, 2011 2:00 pm |
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OK if the line "Heading in degrees=" does not appear you have an RS232
problem. I assume this going to a PC?
- If so, how is the PIC connected to the PC?
- What is between the PIC and PC?
- What are you using for a terminal program on the PC?
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autova
Joined: 24 May 2011
Posts: 14
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| Posted: Tue May 24, 2011 2:25 pm |
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First I'm using the startup kit bought from bizchip. You can check the item here.
40 pin pic startup kit
http://www.bizchip.com/kits.html
Between pic and pc using a serial port cable.
Last I'm using the hyper terminal for showing result. |
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dyeatman
Joined: 06 Sep 2003
Posts: 1934
Location: Norman, OK
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| Posted: Tue May 24, 2011 5:23 pm |
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I can't find a detailed description but the kit indicates it has an RS232
interface. If that's the case the problem must be the baud rate being off
somehow.
I would first get rid of Hyperterminal and use something else like Teraterm
http://hp.vector.co.jp/authors/VA002416/teraterm.html
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autova
Joined: 24 May 2011
Posts: 14
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| Posted: Wed May 25, 2011 12:29 am |
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| what do you mean by baud rate being off somehow ??? sorry for asking to much . |
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dyeatman
Joined: 06 Sep 2003
Posts: 1934
Location: Norman, OK
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| Posted: Wed May 25, 2011 8:41 am |
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The speed at which the two "talk" to each other is the baud rate. If the
speed (in this case 9600 baud) is not the same, the two cannot understand
each other and you get garbage. The allowed difference between the two
systems can be from 1-2% up to as much as 10% depending on the
systems involved and their tolerance but you want it below 2%.
Have you checked your terminal program to see if it is set to 9600 No Parity,
8 Bits and 1 stop bit? That's is what your PIC is set to currently.
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