MSP430 SD Card High Speed Communication

Ionut Ungureanu

Other Parts Discussed in Thread: MSP430F2618

Hello all!

I am currently working at a logger. I am using MSP430F2618 MCU to communicate with a SDHC and everything is fine at low speed. If I raise the speed, all commands return 0x01.

Here are some code snippets:

Clock initialization:

 BCSCTL1 &= ~XT2OFF; // Activate XT2 high freq xtal
 BCSCTL3 |= XT2S_2; // 3 - 16MHz crystal or resonator

 BCSCTL1 = CALBC1_16MHZ;
 DCOCTL = CALDCO_16MHZ;
 // Wait for xtal to stabilize
 do
 {
 IFG1 &= ~OFIFG; // Clear OSCFault flag
 for (idx = 0xFF; idx > 0; idx--); // Time for flag to set
 }while ((IFG1 & OFIFG)); // OSCFault flag still set?
 
 BCSCTL2 |= SELM_2 | SELS; // MCLK = XT2 HF XTAL (safe), SMCLK = XT2

Then I initialize SPI communication. I set first the USCIB_0 registers:

 UCB0CTL1 |= UCSWRST;
 UCB0CTL0 |= UCMST+UCSYNC+UCCKPL+UCMSB; //3-pin, 8-bit SPI master
 UCB0CTL1 |= UCSSEL_2; // SMCLK
 UCB0BR0 = 0x28;                // /40 => around 400Khz with 16Mhz oscillator
 UCB0BR1 = 0; //
 UCB0CTL1 &= ~UCSWRST; // **Initialize USCI state machine**
 P3SEL |= 0x0E; // P3.3,2,1 option select
 P3DIR |= 0x0B;

I am following the steps described in SD Card specifications to initialize the card. Everything goes well and then I am trying to raise the speed by setting UCB0BR0:

 UCB0BR0 = 0x02;             // Divide SMCLK with 2

Next step is to read first sector of the card. But here comes the problem. The response of CMD17 is 0x01.

BUT if I don't change UCB0BR0 value, everything goes well and I am successfully reading/writing on SD card.

Can anyoane help me?

Thanks!

over 12 years ago

0 Jens-Michael Gross over 12 years ago

Guru 227245 points

It should work. I had it working with the 1611 on 4MHz without problems. And with 16MHz (!) on a 5438 (but not thoroughly tested).

Maybe you have too much parasitic capacitance on teh wiring, or the supply voltage is too low for the high speed.

Try a few intermediate steps. Does it work with 1MHz? 2?

How do you change UCB0BR0? ou need to set UCSWRST before and clear it after the change.

0 Ionut Ungureanu over 12 years ago in reply to Jens-Michael Gross

Prodigy 90 points

Thanks for your reply Jens!

So... after the initialization is done, I just set UCB0BR0.

I have tried to raise the speed as you said. Everything goes well until 4Mhz. The response for commands is 0x0.

But after 4Mhz I have to send the commands into a loop in order to get 0x0 response. It usually get the response after 10-15 times.

Plus... at 16Mhz, when I try to read a block, after 20-30 times of sending CMD17 I get the response 0x0, but the actual data is wrong. I receive only 0xFF.

Something is very, very strange. Do you have any idea? :-s

0 Jens-Michael Gross over 12 years ago in reply to Ionut Ungureanu

Guru 227245 points

Ionut Ungureanu said:
So... after the initialization is done, I just set UCB0BR0.

To change UCB0BR0, you must first set UCSWRST, then change UCB0BR0, then clear UCSWRST. THi swill also clear any IE bits, clear the RXIFG bit and set the TXIFG bit.

If oyu just change UCBR0, the already running internal state machine may or may not update properly. Perhaps on frequencies <4MHz (or on BR0>4) this i snot a problem, but maybe the device needs to init differently if BR <4. And by omitting the SWRST, this different init isn't done and transfers don't happen properly.

0 Ionut Ungureanu over 12 years ago in reply to Jens-Michael Gross

Prodigy 90 points

Thanks for the suggestion Jens! I will try this and come back with an answer.

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MSP430 SD Card High Speed Communication