Memory Card Interfacing with PIC Micro-Controller

Memory card (also called a flash memory card) is a solid-state electronic data storage device. Memory cards save the stored data even after the memory device is disconnected from its power source. This ability to retain data is the key
for flash memory card applications, for example, in digital cameras, where the saved pictures are not lost after the memory card is removed from the camera.

For reading and writing to memory cards, one can use out of two protocols and they are:

• SD Card Protocol
• SPI Protocol

SD Card protocol is little bit complex and SPI Protocol is easy as SPI Modules can be found in almost every controller.

Two Activate the SPI Protocol mode of Memory Card just give a low pulse on the Chip Select pin of the Memory Card.

Have a look at the schematic diagram below, to interface memory card with PIC Micro-Controller.

Memory Card Interfacing with PIC Micro-Controller

The Memory Card uses SPI Protocol for reading and writing data to it, apart from that, if you want that a Operating system like Windows, Linux etc can see the contents of the card easily then you have create a FAT table in your memory card, which it self is a very complex process and and writing everything from scratch is itself a project of at-least of one year.
But it didn't means that we are going to take 1 year to complete this project, we will just take few hours.
How? With mikroC Compiler, this compiler has in built library for Memory Card so we have to just use the functions, which are very easy to use and learn.

In this project we are going to create a log in memory card of the temperature sensed by Micro-Controller.
Have a look at the schematic diagram below, which shows how i wired up the things, make sure that when making a real hardware dont forget to make a voltage divider when interfacing memory card and pic micro-controller, as 5V on memory card pins will damage that.

Schematic Diagram

Code is as follow:

 #define BUFFER_SIZE 15  
 //Memory Card Chip Select Connection  
 sfr sbit Mmc_Chip_Select at RB2_bit;  
 sfr sbit Mmc_Chip_Select_Direction at TRISB2_bit;  
 //  
 // LCD module connections  
 sbit LCD_RS at RD0_bit;  
 sbit LCD_RW at RD1_bit;  
 sbit LCD_EN at RD2_bit;  
 sbit LCD_D4 at RD4_bit;  
 sbit LCD_D5 at RD5_bit;  
 sbit LCD_D6 at RD6_bit;  
 sbit LCD_D7 at RD7_bit;  
 sbit LCD_RS_Direction at TRISD0_bit;  
 sbit LCD_EN_Direction at TRISD2_bit;  
 sbit LCD_D4_Direction at TRISD4_bit;  
 sbit LCD_D5_Direction at TRISD5_bit;  
 sbit LCD_D6_Direction at TRISD6_bit;  
 sbit LCD_D7_Direction at TRISD7_bit;  
 // End LCD module connections  
 unsigned char filename[] = "Temp.TXT";  
 unsigned char error;  
 unsigned char i;  
 unsigned int adc_value;  
 unsigned char Temperature_Log[BUFFER_SIZE];  
 void main()  
 {  
  unsigned char ones,tens,hundreds;  
  unsigned int temp;  
  TRISD = 0x00;  
  Lcd_Init();  
  Lcd_Cmd(_LCD_CURSOR_OFF);  
  Lcd_Cmd(_LCD_CLEAR);  
  Delay_ms(100);  
  Lcd_Out(1,1," TEMP. RECORDER");  
  Lcd_Out(2,1," EMBEDDED LAB");  
  Delay_ms(1000);  
  ADCON0 = 0b00000001;  //A/D Converter Power Up  
  ADCON1 = 0x00;     //All Analog Channels  
  ADCON2 = 0b10111110;  //Right Justfied and Slowest Clock for better accuracy  
  ADC_Init();  
  SPI1_Init();  
  SPI1_Init_Advanced(_SPI_MASTER_OSC_DIV64, _SPI_DATA_SAMPLE_MIDDLE, _SPI_CLK_IDLE_LOW, _SPI_LOW_2_HIGH);  
  Delay_us(10);  
  error = MMC_Init();  
  while(error == 1)  
  {  
  Lcd_Cmd(_LCD_CLEAR);  
  Lcd_Out(1,1," CARD NOT FOUND");  
  error = MMC_Init();  
  }  
  Lcd_Cmd(_LCD_CLEAR);  
  Lcd_Out(1,1," CARD DETECTED!");  
  Lcd_Out(2,1,"CARD INITIALIZED");  
  Delay_ms(1000);  
  MMC_Fat_Init();  
  SPI1_Init_Advanced(_SPI_MASTER_OSC_DIV4, _SPI_DATA_SAMPLE_MIDDLE, _SPI_CLK_IDLE_LOW, _SPI_LOW_2_HIGH);  
  Mmc_Fat_Assign(&filename,0xA0);  
  Lcd_Cmd(_LCD_CLEAR);  
  Lcd_Out(1,1,"TEMPERATURE:");  
  while(1)  
  {  
  adc_value = ADC_Read(0);   //Read Temperature from ADC  
  adc_value = adc_value*488;  
  adc_value = adc_value/10;  
  temp = adc_value/100;  
  Temperature_Log[0] = 'T';  
  Temperature_Log[1] = 'E';  
  Temperature_Log[2] = 'M';  
  Temperature_Log[3] = 'P';  
  Temperature_Log[4] = '=';  
  ones = temp%10;  
  temp = temp/10;  
  tens = temp%10;  
  temp = temp/10;  
  hundreds = temp%10;  
  ones = ones|0x30;  
  tens = tens|0x30;  
  hundreds = hundreds|0x30;  
  Temperature_Log[5] = hundreds;  
  Temperature_Log[6] = tens;  
  Temperature_Log[7] = ones;  
  Temperature_Log[8] = '.';  
  Lcd_Chr(2,1,hundreds);  
  Lcd_Chr(2,2,tens);  
  Lcd_Chr(2,3,ones);  
  ones = adc_value%10;  
  adc_value = adc_value/10;  
  tens = adc_value%10;  
  ones = ones|0x30;  
  tens = tens|0x30;  
  Temperature_Log[9] = tens;  
  Temperature_Log[10] = ones;  
  Temperature_Log[11] = ' ';  
  Temperature_Log[12] = 'C';  
  Temperature_Log[13] = '\r';  
  Temperature_Log[14] = '\n';  
  Lcd_Chr(2,4,'.');  
  Lcd_Chr(2,5,tens);  
  Lcd_Chr(2,6,ones);  
  Lcd_Chr(2,7,223);  
  Lcd_Chr(2,8,'C');  
  Mmc_Fat_Append();  
  Mmc_Fat_Write(Temperature_Log,15);  
  Delay_ms(300);  
  }  
 }  

The Log created in memory card when seen in windows explorer is as follow:

Log Data

Video Demonstration:

Creating Image for Memory Card in Simulation Environment (Proteus):

Code Update:
In this project, time and date information are added, so that one can use the log created in memory card for some visual representation with respect to time and date.
A Software is also developed in MATLAB, which takes the log and then plot the Temperature With Respect to time. Have a look at the following video for demonstration.

A Software is also developed in LabVIEW (Similar to the one shown above in MATLAB), which takes the log file as input and then plot the Temperature With Respect to time.

To Download Initial Release Click Here.
To Download the Updated Release with Time and Date addition, Click Here