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amjad_alahdal
Joined: 19 Feb 2013
Posts: 50
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| HMC5843 with Logic Converter |
 Posted: Fri Mar 01, 2013 10:19 am |
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I have a problem with connection my PIC with the HMC5843 with Logic Converter.
HMC5843 like
https://www.sparkfun.com/products/9371
Logic Converter like
https://www.sparkfun.com/products/8745
The connection is like this :
The Pic and the compass have separated voltage source.
the HMC5843 is connected to 3 volt
and the PIC is connected to 5 volt
Then, I connected the SDA and SCL as the following :
each like is connected to the VCC by a resistance of 10 K ohm to the SDA Pin and then to the TX of the logic converter
and then the TX of the other side of the logic converter is connected directly to the PIC
the SCL has the same connection
I wrote the program :
| Code: |
#include<18f2550.h>
#fuses HS,NOPROTECT,NOWDT,NOLVP
#use delay(clock = 8000000)
#use I2C(MASTER, sda=PIN_B0, scl=PIN_B1)
void main()
{
int32 data,data_x,data_y,data_z ;
lcd_init(true);
delay_ms(1000);
printf("Welcome!!!");
delay_ms(1000);
lcd_clear();
printf("It will start now");
delay_ms(2000);
i2c_start();
i2c_write(0x3C);
i2c_write(0x02);
i2c_start();
i2c_write(0x3D);
data=i2c_read(0);
i2c_stop();
lcd_clear();
delay_ms(100);
printf("Block1");
delay_ms(1000);
i2c_start();
i2c_write(0x3C);
i2c_write(0x02);
i2c_write(0x00);
i2c_stop();
lcd_clear();
printf("x:");
lcd_cursor_move(1,9);
printf("Y:");
lcd_cursor_move(2,1);
printf("Z:");
while(true) {
i2c_start();
i2c_write(0x3C);
i2c_write(0x03);
i2c_write(0x3D);
data_x = i2c_read(0)<<8; //msb
data_x |= i2c_read(0);
data_y = i2c_read(0)<<8; //msb
data_y |= i2c_read(0);
data_z = i2c_read(0)<<8; //msb
data_z |= i2c_read(0);
i2c_stop();
delay_ms(100);
lcd_cursor_move(1,3);
printf("%Ld ",data_x);
lcd_cursor_move(1,12);
printf("%Ld ",data_y);
lcd_cursor_move(2,4);
printf("%Ld ",data_z);
delay_ms(1000);
}
}
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Regardless to the function :
lcd_cursor_move and lcd_clear .
I don't get results.
Where are my mistakes. |
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Mike Walne
Joined: 19 Feb 2004
Posts: 1785
Location: Boston Spa UK
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| Posted: Fri Mar 01, 2013 10:46 am |
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I, for one, don't understand.
I need a schematic of exactly what you've done.
(ASCII art will do.)
Mike |
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amjad_alahdal
Joined: 19 Feb 2013
Posts: 50
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| Posted: Fri Mar 01, 2013 10:47 am |
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I'm drawing what I have done using the Proteus , it's taking me some time
please wait |
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Mike Walne
Joined: 19 Feb 2004
Posts: 1785
Location: Boston Spa UK
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| Posted: Fri Mar 01, 2013 10:49 am |
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Please only quote results from real hardware, not Proteus.
Mike |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19520
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| Posted: Fri Mar 01, 2013 10:59 am |
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Several things leaping out.
First the PIC side of the converter also needs pullups. Say 4K7 to 5v.
Second in your read loop, you try to turn the bus round, but don't send the restart needed to do this.
Then third, you should not send 0 to every read transaction. Just I2c_read(), except the last transaction on a block, which wants the zero.
He is saying he is inputting the schematic to Proteus, so he can post it. The fact it isn't in Proteus already, says he is not simulating via Isis, so is OK here.... 
Best Wishes |
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amjad_alahdal
Joined: 19 Feb 2013
Posts: 50
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Ttelmah
Joined: 11 Mar 2010
Posts: 19520
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| Posted: Fri Mar 01, 2013 11:50 am |
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Yes. You _need_ the pullups on the PIC side. The PIC when driving I2C, is driving an open collector bus, which _relies_ on the pullups to pull it high. You don't have these.
Fix this, and the software problems and it may well work.
If not, download the I2C bus scanner program (code library), and see if it sees the device. If not you still have a hardware problem.
Best Wishes |
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ezflyr
Joined: 25 Oct 2010
Posts: 1019
Location: Tewksbury, MA
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| Posted: Fri Mar 01, 2013 2:18 pm |
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Hi,
Pull-ups on the PIC side are probably not going to be your problem if you are using the posted logic level converter from Sparkfun. That is a "classic" n-channel MOSFET level converter with pull-ups on both the low and high voltage sides of the gate. The pull-ups that have been mentioned are already included on your converter.
John |
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