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lokken
Joined: 21 Feb 2010
Posts: 17
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| Reading and writing problem with SD card |
 Posted: Sun Mar 28, 2010 4:25 am |
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I have compiled this code:
| Code: |
#include <18f452.h>
#FUSES NOWDT //No Watch Dog Timer
#FUSES HS //High speed Osc (> 4mhz)
#FUSES NOPROTECT //Code not protected from reading
#FUSES NOBROWNOUT //Reset when brownout detected
#FUSES NOPUT //No Power Up Timer
#FUSES NODEBUG //No Debug mode for ICD
#FUSES NOLVP //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O
#use delay(clock=20000000)
#include <HDM64GS12x.c>
#include <graphics.c>
#include <stdlib.h> // for atoi32
#use rs232(baud=9600,parity=N,xmit=PIN_A3,rcv=PIN_B7,bits=8)
#use fast_io(c)
#define MMCSD_PIN_SCL PIN_C3 //o
#define MMCSD_PIN_SDI PIN_C4 //i
#define MMCSD_PIN_SDO PIN_C5 //o
#define MMCSD_PIN_SELECT PIN_C6 //o
#include <mmcsd.c>
#include <input.c>
BYTE value, cmd,a;
int32 address;
void main()
{
char deg1[32];
char deg2[]="Value";
glcd_init(ON);
glcd_fillScreen(off);
a=0;
while(true)
{
glcd_init(ON);
address=0;
value=100;
glcd_text57(0, 50, deg2, 1, ON);
delay_ms(1000);
mmcsd_write_byte(address, value);
mmcsd_flush_buffer();
delay_ms(1000);
mmcsd_read_byte(address, &a);
delay_ms(1000);
sprintf(deg1, "%d",a);
glcd_text57(0, 30, deg1, 1, ON);
delay_ms(1000);
}
}
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And I have seen the correct value (100) on Graphic LCD. When I add this code shown below to this program I couldn't see anyvalue on graphic lcd:
| Code: |
address=512;
value=300;
glcd_text57(0, 50, deg2, 1, ON);
delay_ms(1000);
mmcsd_write_byte(address, value);
mmcsd_flush_buffer();
delay_ms(1000);
mmcsd_read_byte(address, &a);
delay_ms(1000);
sprintf(deg1, "%d",a);
glcd_text57(0, 30, deg1, 1, ON);
delay_ms(1000);
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What should I do? |
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Wayne_
Joined: 10 Oct 2007
Posts: 681
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| Posted: Mon Mar 29, 2010 2:03 am |
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This is probably not related to your problem but
value=300;
What size is value ?
mmcsd_write_byte(address, value);
By the name of the function I would say that you cannot write the value 300  |
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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| Posted: Mon Mar 29, 2010 5:45 am |
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When debugging try to narrow down the problem to as small a change as possible. Now you have changed the two variables 'address' and 'value', what happens if you change only one of these?
As Wayne already indicated a byte can only contain a maximum value of 255, your 300 will not fit.
Most likely the problem is caused by the write to the SD card failing. The read and write functions do return a result code. Add a check in your program to test for this result value and show an error code on failure.
Also post your compiler version number. |
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lokken
Joined: 21 Feb 2010
Posts: 17
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| Posted: Thu Apr 01, 2010 7:51 am |
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I will ask one more simple question.
Are these explanations true?(MY compiler version is 4.068)
| Code: |
mmcsd_write_byte(address, value); /// 0.adress=value
mmcsd_read_byte(address, &a); /// a=0.adress |
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theasus
Joined: 31 May 2009
Posts: 79
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| Posted: Thu Apr 01, 2010 12:43 pm |
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I have same problem with lokken.I want to use SD card as a large EEPROM. But I couldn't understand usage of these codes:
| Code: |
mmcsd_write_byte(address, value);
mmcsd_read_byte(address, &a);
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Apr 01, 2010 12:54 pm |
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| Quote: |
I have same problem with lokken. I want to use SD card as a large
EEPROM. But I couldn't understand usage of these codes:
mmcsd_write_byte(address, value);
mmcsd_read_byte(address, &a);
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Look at the comments in this file:
| Quote: | | c:\program files\picc\drivers\mmcsd.c |
It says:
| Quote: |
//// mmcsd_flush_buffer()
//// The two user write functions (mmcsd_write_byte() and
//// mmcsd_write_data()) maintain a buffer to speed up the writing
//// process. Whenever a read or write is performed, the write
//// buffer is loaded with the specified page and only the
//// contents of this buffer is changed. If any future writes
//// cross a page boundary then the buffer in RAM is written
//// to the MMC/SD and then the next page is loaded into the
//// buffer. mmcsd_flush_buffer() forces the contents in RAM
//// to the MMC/SD card. Returns 0 if OK, non-zero if errror.
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theasus
Joined: 31 May 2009
Posts: 79
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| Posted: Sat Apr 03, 2010 11:23 am |
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Ok I have read the functions but i didn't understand one point.
Why are we using pointer for getting a value from any address? |
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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| Posted: Sun Apr 04, 2010 6:26 am |
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| theasus wrote: | | Why are we using pointer for getting a value from any address? |
You mean, why was the function not defined as: value = mmcsd_read_byte(int32 address)
Only the original author can answer this question, but I think it was implemented like this because there is also the error code to be returned. You can only return a single value and because all other functions return an error code it made more sense to do the same here as well. |
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