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DDDDaniel
Guest
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 Posted: Sun Feb 03, 2008 1:01 pm |
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that's strange... in my last posting the for-loops got corrupted.
it has to be:
for(i=0 ; i<12 ; i++)
and
for (a = 0 ; a<0x06 ; a++)
of course... |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sun Feb 03, 2008 1:05 pm |
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You have to disable HTML when you post code.
My advice:
1. Register and become a forum member.
2. Edit your profile and permanently disable HTML.
3. Keep BBcode enabled.
4. Log in and select the tick box to "log in automatically every time".
Then you'll never have to worry about disabling HTML. It will
always be done. Your code will always post correctly. |
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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| Posted: Sun Feb 03, 2008 6:00 pm |
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| Code: | // send 6 Byte Command
for (a = 0;a<0x06> 500)
{
break; //abort. MMC/SD-card does not response
}
} |
There is more corrupted code here than just the for-loop. Looks like some lines are missing. Same for the other for-loop.
Too bad you are not a register member of this forum or you would have had the option to edit your previous posting.
I'm glad to hear your read speed increased from 260kB/s to 540kB/s, a nice improvement!
It is indeed fun to squeeze out the last bit of power from the PIC processor, but it also helps a lot to learn understand the processor better. For example I never expected one SPI mode to be faster than another.
I'm willing to help improve your write routine, but with all the new knowledge you should be able to make some huge improvements yourself. Then return to this forum for the final tweaking. |
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ColtFish
Joined: 04 Feb 2008
Posts: 3
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| Posted: Mon Feb 04, 2008 1:16 pm |
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Allright,
here's the complete MMC/SD - code, this time with HTML disabled 
| Code: |
#byte SSP1CON1 = 0xFC6
#byte SSP1STAT = 0xFC7
#byte SSP1BUF = 0xFC9
// Sends a Command to the MMC/SD-card
int mmc_write_command (int *cmd)
{
int tmp = 0xff;
long Timeout = 0;
int a;
MMC_Enable();
// send 8 Clock pulses
spi_write(0xFF);
// send 6 Byte Command
for (a = 0;a<0x06;a++)
{
spi_write(*cmd++);
}
// wait for a valid reponse
while (tmp == 0xff)
{
tmp = spi_read(0xFF);
if (Timeout++ > 500)
{
break; //abort. MMC/SD-card does not respond
}
}
return(tmp);
}
int mmc_init()
{
int i;
unsigned long Timeout = 0;
unsigned int res;
int cmd[] = {0x40,0x00,0x00,0x00,0x00,0x95};
// setup SPI Mode 3 (CKP = 1, CKE = 0)
SSP1STAT = 0b00000000; // cke = 0
SSP1CON1 = 0b00110010; // sspen = 1, SPI-FREQ: FOSC/64, CKP = 0
output_high(CS_CARD);
delay_cycles(255);
// initialise the MMC card into SPI mode by sending clock pulses
for(i=0;i<12;i++)
{
SPI_WRITE(0xFF);
}
while(mmc_write_command (CMD) !=1)
{
delay_ms(1);
if (Timeout++ > 0x2FFF)
{
return(1); // Failure! (Return Code1)
}
}
// Send Command CMD1 to MMC/SD-card
Timeout = 0;
CMD[0] = 0x41;//Command 1
CMD[5] = 0xFF;
res = mmc_write_command (CMD);
while( res !=0)
{
res = mmc_write_command (CMD);
delay_ms(1);
if (Timeout++ > 0x2FFF)
{
printf("\n\rInit failed. [%X]", res);
return(2); //Failure! (Return Code2)
}
}
printf("\n\rInit done.");
// after successful mmc-init the SPI Frequency can be set to maximum speed (Fosc/4)
// Mode 3 (CKP = 1, CKE = 0)
SSP1STAT = 0b00000000; // cke = 0
SSP1CON1 = 0b00110000; // sspen = 1, SPI_CLK_DIV_4, CKP = 0
// disable MMC/SD-card chipselect
MMC_Disable();
return(0);
}
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...an optimized version of my sector_write code will follow soon
Best wishes,
Daniel |
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metalm
Joined: 22 Mar 2007
Posts: 23
Location: Buenos Aires, Argentina
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| Posted: Wed Feb 13, 2008 7:49 am |
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Helo, me again
What if you enable the READ_BLK_MISALIGN parameter? this permits crossing block boundaries and then there is no need to bufferize an entire block?
also, i use the "multiread" comand, for reading continuous block at the max speed possible |
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ColtFish
Joined: 04 Feb 2008
Posts: 3
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| Posted: Wed Feb 13, 2008 9:29 am |
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Hey metalm,
thanks for your input!
I need the sd card access functions for a USB mass storage device so the block length is fixed.
The "multiread" command might be a nice idea! I'll try to implement this...
Thanks,
daniel |
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peter
Guest
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| Posted: Mon Mar 24, 2008 11:34 am |
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Hi!
I read attentively the 3 pages of this thread and i have a question referred frequency clock SPI hardware SCK of MSSP module.
datasheet on 18F4550 said maximum speed SCK of 12Mhz (Fosc/4), but the crystal then must be 48Mhz???
if xtal=48Mhz then initializations MMC working above 400Khz (mode Fosc/64 more slow possible)
working xtal=24Mhz, i have 24Mhz / 64 = 375Khz necessary for init MMC, but speed clock up 24Mhz / 4 = 6Mhz maximum :(
i want working SCK to 12Mhz and using SPI hardware 18F4550
any idea? |
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ColtFish
Joined: 04 Feb 2008
Posts: 3
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| Posted: Mon Mar 24, 2008 12:34 pm |
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All cards I'm working with initialize without any problems when I slow down the SPI Frequency to Fosc/64 = 750kHz.
Obviously it is not necessary to reduce SPI speed any further.
For the future, you should take a look at the PIC18FX7j50 device family which comes with a software switchable PLL which would enable you to reduce the SPI speed to <= 400kHz and the cpu could be running at 48MHz during normal operation.
best regards,
daniel |
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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| Posted: Mon Mar 24, 2008 3:21 pm |
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It's very well possible the newer cards will accept a higher start-up clock rate. I haven't read the newer MMC specifications.
An alternative method to generate the slow SPI signal is to use a software based SPI driver for the start-up phase and then switch to the hardware SPI for fast transmissions.
In the v4.xxx compiler versions the software driver is easy to setup using the #USE SPI command, specifying the bitrate using the BAUD keyword.
In older compiler versions a software SPI driver example can be found in the CCS driver mmc_spi.c (included with the v3.249 compiler.) |
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peter
Joined: 25 Mar 2008
Posts: 2
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| Posted: Tue Mar 25, 2008 10:48 am |
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| ColtFish wrote: | All cards I'm working with initialize without any problems ...For the future, you should take a look at the PIC18FX7j50 device family which comes with a software switchable PLL which would enable you to reduce the SPI speed to <= 400kHz and the cpu could be running at 48MHz during normal operation.
best regards,
daniel |
cpu running 48Mhz in fuses (XT/HS)PLL, but MSSP module configured SPI, SCK working directly with Crystal Frecuency
i thought that e.j. crystal 4Mhz i have 48Mhz using PLL and CPU microcontroller run this speed, but i read specification MSSP, it said SCLK working Fosc/4 maximun
then I would that using in Fosc a clock frecuency running to 48Mhz to have 12Mhz in SCK to increase speed in communication to MMC
ckielstra i will study your idea for when i change speed from init to stage read/write block. thanks you |
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Ttelmah
Guest
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| Posted: Tue Mar 25, 2008 11:19 am |
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Designed to confuse you, but on these chips, 'Fosc', is _not_ always the external oscillator frequency. Look at the clock diagram. A series of clocks are generated. One for USB, one for the CPU, and one for the peripherals. This last, is 'Fosc' in MicroChip parlance, even if it does not come directly from the external oscillator. It is made (sort of) clear in several places, where Fosc/4, is used a a direct alternative to the instruction rate, and in the 'timing specification' table, where Fosc, is given as being the external oscillator frequency, with a big note at the bottom (paraphrased), that 'Tcy' (1/Fosc) is the external oscillator frequency, _except_ in PLL modes.
Best Wishes |
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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| Posted: Tue Mar 25, 2008 9:39 pm |
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| ckielstra wrote: | | It's very well possible the newer cards will accept a higher start-up clock rate. I haven't read the newer MMC specifications. |
I just found out the new MMC specifications v4.3 is now available free of charge at http://www.mmca.org/compliance/buy_spec/.
According to chapter 12.7.1 the Identification Mode still has the slow clock speed of 400kHz, with a tolerance of +20kHz. |
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peter
Joined: 25 Mar 2008
Posts: 2
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| Posted: Sat May 17, 2008 1:43 pm |
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Hi!
to pic´s series 18F with features switch clock "in hot", you can use OSCCON SFR to reducing speed Fosc durign mmc initializations.
code here:
| Code: |
mmc_init()
{
// speed low to SCK=125Khz
setup_oscillator(OSC_INTRC |OSC_8MHZ);
// change system oscillator to INTRC = 8 MHz
// IESO bit ignored
delay_cycles(10); // transition 7 cycles + extra
while(!IOFS){} // wait stabilization Fosc
setup_spi(SPI_MASTER | SPI_H_TO_L | SPI_CLK_DIV_64 | SPI_XMIT_L_TO_H);
// spi for hardware, master, Fosc/64, clock idle high, falling edge
...
output_high(chip_select);
delay_ms(100); // power-up timer for MMC
...
...
...
// increase speed SCK=12Mhz
setup_oscillator(OSC_NORMAL);
// change system Oscillator to primary oscillator = Xtal
setup_spi(SPI_MASTER | SPI_H_TO_L | SPI_CLK_DIV_4 | SPI_XMIT_L_TO_H);
// spi for hardware, master Fosc/4, clock idle high, falling edge
...
}
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