1 Hardware Description
CS
DI
VSS
VCC
SCK
CD
DO
1
2
3
4
5
6
7
3 V
47 kW
100 nF
3 V
0.1 µF
P5.0
P5.1/SIMO1
P5.3/UCLK1
P5.6
P5.2/SOMI1
RST
DVCC
AVCC
DVSS
AVSS
MSP430F161x
MMC Card
47 kW
Application Report
SLAA281B–November 2005–Revised March 2008
Interfacing the MSP430
With MMC/SD Flash Memory Cards
Stefan Schauer, Christian Speck.............................................................................................. MSP430
ABSTRACT
This application report and the associated source code files demonstrate the
implementation of a serial peripheral interface (SPI) between the MSP430F161x
microcontroller and an MMC or SD flash memory card used in SPI mode. The provided
information can be used with any MSP430 device with a hardware SPI interface.
The MSP430F161x is used to communicate with the MMC or SD card via the SPI interface. SPI is a fast
and efficient protocol that allows for simultaneous bidirectional data transfer. Serial data is transmitted and
received by the MSP430 using the USART module in SPI mode. The hardware interconnection for the
master-slave configuration operating on a single supply voltage is shown in Figure 1.
The associated MSP430F161x pins P5.3 and P5.4 are configured as GPIO to control the chip-select pin
and read the memory card detect signal. The USART1 hardware peripheral of the MSP430F161x is
configured in the 3-pin SPI mode. Pins P5.1, P5.2, and P5.3 of the MSP430 provide the SIMO1, SOMI1,
and UCLK1 interface to the MMC card.
Figure 1. Connection Between MSP430 and MMC Card
SLAA281B–November 2005–Revised March 2008 Interfacing the MSP430 With MMC/SD Flash Memory Cards 1
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2 Software Description
3 Function Description
3.1 char mmcInit (void);
3.2 char mmcping(void);
3.3 void mmcSendCmd (const char cmd, unsigned long data, const char crc);
Software Description
The code associated with this application note is designed as a driver set for communication between an
MSP430 and an MMC card or an SD card via the SPI bus as illustrated in the preceding hardware section.
The code is written modularly and can be reused easily. Note that only a subset of the available card
commands is used, based on the limitations of the SPI interface and the secure functions of the SD card.
An example main() function is provided to illustrate proper use of the driver functions. It initializes the
MSP430F161x in the 3-pin SPI mode with the function mmcInit(). The MSP430 then polls until an MMC
card is detected and tries to read the device memory size. Upon the completion, the MSP430 prepares a
buffer with 512 bytes of data and writes it into two different sectors of the card. Finally, the MSP430 reads
the data back that was written to each memory segment.
After uncommenting the code line:
//#define withDMA
the MSP430F161x DMA module is used for data transmission between the MSP430 and the MMC card,
resulting in higher communication speed and less CPU load.
If the software is adapted to a different USART or a different device in which the USART is connected to
other port pins, the following functions must be checked for the correct settings:
• void initSPI (void)
• char mmcInit (void)
• mmc.h file
Initialize the port, SPI, and the MMC card. This routine may need to be adjusted if the library is adapted to
another MSP430 type or to another USART module. Also, some of the control signals can be set to a
different port, if necessary.
Parameter: None
Return: Status Error/success code
Check if MMC card is present.
Parameter: None
Return: Status Error/success code
Send a command to the MMC card.
Parameter: cmd Command that should be sent to the MMC card
data Data for the command
crc Checksum for the command
Return: None
Interfacing the MSP430 With MMC/SD Flash Memory Cards2 SLAA281B–November 2005–Revised March 2008
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3.4 char mmcGoIdle();
3.5 char mmcSetBlockLength (const unsigned long);
3.6 char mmcReadBlock(const unsigned long address, const unsigned long count,
3.7 char mmcWriteBlock (const unsigned long address, const unsigned long count,
Function Description
Set the MMC card in idle mode to save current.
Parameter: None
Return: Status Error/success code
Set the MMC block length of count = 2n byte. Normally this command is not required. The default block
length is 512 bytes.
Parameter: Block Length of count = 2n Byte
Return: Status Error/success code
unsigned char *pBuffer);
#define mmcReadSector(sector, pBuffer) mmcReadBlock(sector × 512, 512, pBuffer)
Read a size byte big block beginning at the address.
Parameter: address Start address of data to read on the card
count Number of bytes to read
pBuffer Pointer to read buffer
Return: Status Error/success code
unsigned char *pBuffer);
#define mmcWriteSector(sector, pBuffer) mmcWriteBlock(sector × 512, 512, pBuffer).
Write a 512 byte big block beginning at the (aligned) address
Parameter: address Start address of data to read on the card
count Number of bytes to write
pBuffer Pointer to write buffer
Return: Status Error/success code
SLAA281B–November 2005–Revised March 2008 Interfacing the MSP430 With MMC/SD Flash Memory Cards 3
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3.8 char mmcReadRegister (const char cmd_register, const unsigned char length,
3.9 unsigned long mmcReadCardSize(void);
4 References
References
unsigned char *pBuffer);
Read the Register arg1 with Length arg2 (into the buffer).
Parameter: cmd_register Register to read
length Number of bytes to read
pBuffer Pointer to read buffer
Return: Status Error/success code
Read the card size from the CSD Register.
Parameter: None
Return: Detected card size
1. MSP430x169 Mixed Signal Microcontroller Data Sheet (SLAS368)
2. MSP430x1xx Family User’s Guide (SLAU049)
3. SanDisk MultiMediaCard Product Manual (SanDisk, 2001)
4 Interfacing the MSP430 With MMC/SD Flash Memory Cards SLAA281B–November 2005–Revised March 2008
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1 Hardware Description
2 Software Description
3 Function Description
3.1 char mmcInit (void);
3.2 char mmcping(void);
3.3 void mmcSendCmd (const char cmd, unsigned long data, const char crc);
3.4 char mmcGoIdle();
3.5 char mmcSetBlockLength (const unsigned long);
3.6 char mmcReadBlock(const unsigned long address, const unsigned long count, unsigned char *pBuffer);
3.7 char mmcWriteBlock (const unsigned long address, const unsigned long count, unsigned char *pBuffer);
3.8 char mmcReadRegister (const char cmd_register, const unsigned char length, unsigned char *pBuffer);
3.9 unsigned long mmcReadCardSize(void);
4 References