1. Build a microSD Bootloader using a PIC microcontroller
Bootloader Firmware Design
02/06/2013 Fred Eady

2. Bootloader Firmware Topics
BOOTLOADER HARDWARE MAPPING
HardwareProfile.h
microSD Card SPI Portal
LCD Controls/LCD SPI Portal
Push Buttons
BOOTLOADER FILES
BOOTLOADER OPERATION
SUMMARY

3. Bootloader Firmware Topics
BOOTLOADER HARDWARE MAPPING
HardwareProfile.h
microSD Card SPI Portal
LCD Controls/LCD SPI Portal
Push Buttons
BOOTLOADER FILES
BOOTLOADER OPERATION
SUMMARY

4. Bootloader HardwareProfile.h
microSD CARD SPI PORTAL
#define USE_SD_INTERFACE_WITH_SPI
#define SD_CS LATDbits.LATD0
#define SD_CS_TRIS TRISDbits.TRISD0
#define SPICLOCK TRISCbits.TRISC3
#define SPIIN TRISCbits.TRISC4
#define SPIOUT TRISCbits.TRISC5
#define SPICLOCKLAT LATCbits.LATC3
#define SPIINLAT LATCbits.LATC4
#define SPIOUTLAT LATCbits.LATC5
#define SPICLOCKPORT PORTCbits.RC3
#define SPIINPORT PORTCbits.RC4

5. Bootloader HardwareProfile.h
PIC18F47J13 SPI1 Module Registers
#define SPICON SSP1CON1
#define SPISTAT SSP1STAT
#define SPIBUF SSP1BUF
#define SPISTAT_RBF SSP1STATbits.BF
#define SPICON1bits SSP1CON1bits
#define SPISTATbits SSP1STATbits
#define SPI_INTERRUPT_FLAG PIR1bits.SSP1IF
#define SPI_INTERRUPT_FLAG_ASM PIR1, 3
#define SPIENABLE SSP1CON1bits.SSPEN

6. Bootloader SD-SPI.c } SD-SPI.c Implements the SD Card API
void MDD_SDSPI_InitIO (void) {
// Turn off the card
SD_CS = 1;
SD_CS_TRIS = OUTPUT; }
SD-SPI.c Implements the SD Card API
MDD_SDSPI_MediaDetect
MDD_SDSPI_MediaInitialize
MDD_SDSPI_ReadCapacity
MDD_SDSPI_ReadSectorSize
MDD_SDSPI_InitIO
MDD_SDSPI_SectorRead
MDD_SDSPI_SectorWrite
MDD_SDSPI_AsyncReadTasks
MDD_SDSPI_AsyncWriteTasks
MDD_SDSPI_WriteProtectState
MDD_SDSPI_ShutdownMedia

7. Bootloader SD-SPI.h SD-SPI.h Contains SPI Init Definitions
#define USE_SD_INTERFACE_WITH_SPI
#ifdef USE_SD_INTERFACE_WITH_SPI
#include "MDD File System/SD-SPI.h"
#endif
SD-SPI.h
Contains SPI Init Definitions
Defines SD Card States
Defines SD Card Command Codes
Defines SD Card Command Structures
Defines SD Card Response Types
Contains Prototypes of API Functions Provided in SD-SPI.c

8. Bootloader Firmware Topics
BOOTLOADER HARDWARE MAPPING
HardwareProfile.h
microSD Card SPI Portal
LCD Controls/LCD SPI Portal
Push Buttons
BOOTLOADER FILES
BOOTLOADER OPERATION
SUMMARY

9. Bootloader LCD Controls
LCD_RST
Active Low Reset Signal
LCD_RS
Register Select Signal
0 – Instruction
1 – Data
LCD_CS
Active Low Chip Select
*SHDN
LCD Power Switch

10. Bootloader HardwareProfile.h
LCD MODULE CONTROL BITS
#define LCD_SHDN_IOLATDbits.LATD4
#define LCD_SHDN_TRISTRISDbits.TRISD4
#define LCD_RSTLATDbits.LATD3
#define LCD_RST_TRISTRISDbits.TRISD3
#define LCD_RSLATDbits.LATD2
#define LCD_RS_TRISTRISDbits.TRISD2
#define LCD_CSLATDbits.LATD1
#define LCD_CS_TRISTRISDbits.TRISD1

11. Bootloader LCD SPI Portal
Code Found in bootio.c
Function: BLIO_InitializeIO
EECON2 = 0x55;
EECON2 = 0xAA;
PPSCONbits.IOLOCK = 0;
RPINR21 = 8;//SDI2 AT RB5 RP8
RPOR6 = 11; //SCK2 AT RB3 RP6
RPOR7 = 10; //SDO2 AT RB4 RP7
PPSCONbits.IOLOCK = 1;

12. Bootloader Firmware Topics
BOOTLOADER HARDWARE MAPPING
HardwareProfile.h
microSD Card SPI Portal
LCD Controls/LCD SPI Portal
Push Buttons
BOOTLOADER FILES
BOOTLOADER OPERATION
SUMMARY

13. Bootloader Pushbuttons
#define BUTTON1PORTDbits.RD5
#define BUTTON1_TRISTRISDbits.TRISD5
#define BUTTON2PORTDbits.RD6
#define BUTTON2_TRISTRISDbits.TRISD6

14. Bootloader Firmware Topics
BOOTLOADER HARDWARE MAPPING
HardwareProfile.h
microSD Card SPI Portal
LCD Controls/LCD SPI Portal
Push Buttons
BOOTLOADER FILES
BOOTLOADER OPERATION
SUMMARY

15. Bootloader Files boot_config.h Defines Application Address
Defines Remapped Interrupt Vector Addresses
Defines Maximum Size of FLASH Block
boot_io.c
Initialize PIC18F47J13 I/O Routines
Functions to Scan Load and Abort Push Buttons
SD-SPI.c
Contains SD Card API
FSIO.c
File System Operations (FSfopen, FSfclose, etc.)
FSconfig.h
Define Locations of Data and FAT Buffers
Defines File System Behavior (ALLOW_FILESEARCH)

16. Bootloader Files boot_load_hex.c
Contains ASCII helper functions for boot_media_msd.c
boot_media_msd.c
Processes Intel HEX File
Programs PIC18F47J13 FLASH with Application Code
xxxxxxxx.hex
A User Generated Intel HEX File Containing the Application Code
HardwareProfile.h
Contains Hardware Mapping for the PIC18F47J13
lcd.c
The LCD Module Driver

17. Bootloader Firmware Topics
BOOTLOADER HARDWARE MAPPING
HardwareProfile.h
microSD Card SPI Portal
LCD Controls/LCD SPI Portal
Push Buttons
BOOTLOADER FILES
BOOTLOADER OPERATION
SUMMARY

18. Bootloader Process
The Original SD-SPI.c API Call Names Are Aliased in FSconfig.h as Follows:
#define MDD_MediaInitialize MDD_SDSPI_MediaInitialize
#define MDD_MediaDetect MDD_SDSPI_MediaDetect
#define MDD_SectorRead MDD_SDSPI_SectorRead
#define MDD_SectorWrite MDD_SDSPI_SectorWrite
#define MDD_InitIO MDD_SDSPI_InitIO
#define MDD_ShutdownMedia MDD_SDSPI_ShutdownMedia
#define MDD_WriteProtectState MDD_SDSPI_WriteProtectState
#define MDD_ReadSectorSize MDD_SDSPI_ReadSectorSize
#define MDD_ReadCapacity MDD_SDSPI_ReadCapacity

19. Bootloader Process
The Original SD-SPI.c API and FSIO.c Calls Are Aliased in boot_config.h as Follows:
#define BLMedia_InitializeTransport() FSInit()
#define BLMedia_DeinitializeTransport() TRUE
#define BLMedia_MediumAttached() MDD_MediaDetect()

20. Bootloader Process Remap the Interrupt Vectors
Remapped Interrupt Vector Addresses Found in boot_config.h
#define APPLICATION_HIGH_ISR xA008
#define APPLICATION_LOW_ISR xA018
#pragma code High_ISR = 0x08
void Remapped_High_ISR (void) {
_asm goto APPLICATION_HIGH_ISR _endasm }
#pragma code Low_ISR = 0x18
void Remapped_Low_ISR (void)
_asm goto APPLICATION_LOW_ISR _endasm

21. Bootloader Process Call BLIO_InitializeIO in bootio.c
Disable Analog to Digital Converter
Set TRIS Registers (PORTA-PORTE)
Initialize the LCD Control Pins
Deselect microSD Card at SPI Portal Level
Use Peripheral Pin Select to Enable SPI2 for LCD
Initialize the LCD Module
Display “microSD Bootloader” for 3 Seconds
sLCDInit();
strcpypgm2ram((char*)sLCDText, " microSD Bootloader ");
//strcpypgm2ram((char*)sLCDText, " ");
sLCDUpdate();
DelayMs(3000);

22. Bootloader Process Initialize the LOAD Countdown Timer
Initialize the count array with 0x20
Load the last byte of the count array with 0x00
unsigned char j;
unsigned char count[17];
for(j=0;j<sizeof(count);j++) {
count[j]=' '; }
count[16] = 0x00;

23. Bootloader Process Display “PRESS BUTTON 1 TO LOAD” on Line 1
Alternately Place the Countdown Number at LCD Position 8 on Line 1
j = 0x39;
while (j > 0x30 ) {
i = 0;
count[8] = j;
strcpypgm2ram((char*)sLCDText, " PRESS BUTTON TO LOAD ");
//strcpypgm2ram((char*)sLCDText, " ");
sLCDUpdate();
DelayMs(1000);
sLCDErase();
sLCDWriteLine(1,count);

24. Bootloader Process Check Push Button 1 for a Bootload Request
If the Push Button is Depressed:
Display “Bootloader Enabled”
Wait for Push Button 1 to be Released then Start the Bootload Process
Otherwise, Time Out and Decrement the Count Down Timer
while (i < ) {
// Check to see if the user wants to load new application
if (BLIO_LoaderEnabled() == TRUE)
strcpypgm2ram((char*)sLCDText," Bootloader Enabled ");
//strcpypgm2ram((char*)sLCDText," ");
sLCDUpdate();
while(BLIO_LoaderEnabled() == TRUE){}
LoadApplication(); }
i++;
j--;

25. Bootloader Process BOOL BLIO_LoaderEnabled ( void ) {
TRISDbits.TRISD5 = 1; //BTN1
if (PORTDbits.RD5 == 0)
DelayMs(10);
if(PORTDbits.RD5 == 0)
return 1; }
else
return 0;

26. Bootloader Process
Make Sure microSD Interface to SPI1 is Disabled (MDD_InitIO())
Look for a mounted microSD Card
If Not Found, Inform the User and Keep Looking for a Card or an Abort Command (BTN2 Depressed)
MDD_InitIO();
// Loader main loop
while (LoadingApplication) {
if(BootMediumAttached == 0)
BootMediumInitialized = FALSE;
strcpypgm2ram((char*)sLCDText, " microSD Card Not Found ");
//strcpypgm2ram((char*)sLCDText, " ");
sLCDUpdate();
do{
BootMediumAttached = BLMedia_MediumAttached();
if (BLIO_AbortLoad())
Reset(); }
}while(BootMediumAttached == 0);

27. Bootloader Process Perform a Media Detect (BootMediumAttached)
If Media Detect is TRUE, Perform a Media Initialize Check
If Media is Initialized, Set State Machine to FILE_FETCH and Clear the Error Flag (BootImageFileError)
if (BootMediumAttached) {
// The boot media is attached.
//Make sure the boot meia is also initialized
if (BootMediumInitialized)
//Media is attached and initialized
BootImageFileError = FALSE;
state = FILE_FETCH;

28. Bootloader Process Media Not Mounted
Inform the User and Start the Process Again
Loop Until a microSD Card is Mounted or an Abort Command is Issued (BTN2 Depressed)
else {
//Media was not mounted
BootMediumInitialized = FALSE;
strcpypgm2ram((char*)sLCDText," microSD Card Not Found ");
//strcpypgm2ram((char*)sLCDText," ");
sLCDUpdate(); }

29. Bootloader Process Use FindFirstpgm to Find User Generated .HEX File
Stuff the Filename into fileList Array and Increment filesCounter
while (BootImageFileError == FALSE) {
switch (state)
case FILE_FETCH:
status = FindFirstpgm("*.HEX", ATTR_ARCHIVE | ATTR_READ_ONLY | ATTR_HIDDEN, &searchRecord);
if (status == 0)
// If a file was found, add it to the file list strcpy((char*)&fileList[filesCounter*sizeof(searchRecord.filename)], (const char*)&searchRecord.filename);
filesCounter ++;

30. Bootloader Process Display the Filename if (filesCounter != 0) {
// User .HEX file found
state = SCREEN_UPDATE;
else
BootImageFileError = TRUE; }

31. Bootloader Process case SCREEN_UPDATE: { sLCDErase(); sLCDUpdate();
sprintf(sLineBuf,"Loading");
sLCDWriteLine(1,sLineBuf);
sLCDWriteLine(2,searchRecord.filename);
state = LOAD_IT;
break; }

32. Bootloader Process // Read the boot image file and program it to Flash
if (BLMedia_LoadFile(searchRecord.filename)) {
LoadingApplication = FALSE;
sLCDErase();
sLCDUpdate();
sprintf(sLineBuf,"Launching");
sLCDWriteLine(1,sLineBuf);
sLCDWriteLine(2,searchRecord.filename);
DelayMs(2000);
BootApplication();
state = FILE_FETCH; }
else
BootImageFileError = TRUE;