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Joshua Lai
Joined: 19 Jul 2004
Posts: 42
Location: Malaysia, PJ
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| EEprom sequential read - working! |
 Posted: Tue Sep 20, 2005 7:40 pm |
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I tried writing my own program to write and read eeprom, it is working !!
| Quote: |
#include <16F876.h>
#use delay(clock=20000000)
#use i2c(master,sda=PIN_C4,scl=PIN_C3)
#fuses hs,noprotect,nowdt,nolvp
#byte PORTB=6
int a, r;
main()
{
output_float(PIN_C3); //initialize eeprom
output_float(PIN_C4);
r=0;
set_tris_b(0);
portb=0x01; delay_ms(1000);
portb=0x00; delay_ms(1000);
i2c_start();
i2c_write(0xA0); //control write
i2c_write(0x00); //address (max 7FF8)
i2c_write(0x00);
i2c_write(0x01); //data (max page 64)
i2c_write(0x02);
i2c_write(0x04);
i2c_write(0x10);
i2c_write(0x20);
i2c_write(0x40);
i2c_write(0x80);
i2c_stop();
delay_ms(1000);
i2c_start();
i2c_write(0xA0);
i2c_write(0x00);
i2c_write(0x00);
i2c_start();
i2c_write(0xA1); //control read
for(a=0;a<8;a++)
{ r = i2c_read();
portb=r; delay_ms(1000);
}
portb=0x01; delay_ms(1000);
portb=0x00; delay_ms(1000);
}
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What I actually need to do is abitrary waveform generation. I need to store and read large amount of data in the eeprom, where time accuracy (sampling rate) is very important, fast is important also. So I have to count how much time PIC spent to read the eeprom.
Instead of using the built in driver 24256, I write my own program to read the eeprom. I found that I save at least hundred lines of assembly code.
But I don't really understand the assembly code, does i2c_read() same as sequential read in the eeprom datasheet?
I can also read out the eeprom data using hyperterminal (through PIC). But how can I use hyperterminal to write the eeprom? Because my icprog 1.04 showing error when verifying the eeprom. Type in the data on hyperterminal one by one is too slow. |
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Joshua Lai
Joined: 19 Jul 2004
Posts: 42
Location: Malaysia, PJ
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| Software or Hardware i2c |
| Posted: Fri Sep 23, 2005 11:07 pm |
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PIC 16F876, PCM compliler 2.734
I found that I can use other pins for i2c as well! Previously I thought I can only use pin C3 and C4. What actually hardware i2c and software i2c? What advantages of using hardware or software i2c?
Now I understand that i2c_read(0) is without ACK, i2c_read(1) is with ACK.
I use PIC and hyperterminal to read the eeprom and found all the data inside is correct, although ic-prog failed to verify.
How fast can I read the eeprom to hyperterminal without error? I read the assembly code and found that the PIC will loop until some bit is set, so how to determine about how long to read the eeprom? |
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Joshua Lai
Joined: 19 Jul 2004
Posts: 42
Location: Malaysia, PJ
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| Posted: Wed Sep 28, 2005 9:57 pm |
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| Quote: | #include <16F876.h>
#use delay(clock=20000000)
#fuses hs,noprotect,nowdt,nolvp
#byte PORTB=6
#include <24256.C>
int i,d; long a;
main()
{
d=0;a=0;
set_tris_b(0);
portb=0x01; delay_ms(1000);
portb=0x00; delay_ms(1000);
init_ext_eeprom();
delay_ms(1);
write_ext_eeprom(0,0x02);
d = read_ext_eeprom(0);
portb=d; delay_ms(1000);
for(i=0;i<4;i++) //Write and read 1000 times
{
for(d=0;d<250;d++)
{
write_ext_eeprom(a,d);
d = read_ext_eeprom(a);
portb=d;
a=a+1;
}
}
portb=0x01; delay_ms(1000);
portb=0x00; delay_ms(1000);
for(a=0;a<30000;a++) //Read 30000 times
{
d = read_ext_eeprom(a);
portb=d;
}
portb=0x01; delay_ms(1000);
portb=0x00; delay_ms(1000);
i2c_start();
i2c_write(0xA0);
i2c_write(0x00);
i2c_write(0x00);
i2c_start();
i2c_write(0xA1); //Sequential read 60000 times
for(a=0;a<60000;a++)
{ d = i2c_read();
portb=d;
}
portb=0x01; delay_ms(1000);
portb=0x00; delay_ms(1000);
} |
I tried to measure the time for write/read using the 24256.c driver, and also the sequential read time using i2c directly.
| Quote: |
Write/Read Read Sequential Read
Cycles 1000 30000 60000
Time(s) 5 18 6
Time(us) 5000 600 100
for 1 cycle
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I just looked at the LED and pressed the stopwatch, how to measure more accurately? |
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Mark
Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA
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| Posted: Thu Sep 29, 2005 6:06 am |
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| Toggle a pin and measure with an oscilloscope. |
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