Microchip Technology MPLAB, User Manual

MPLAB Starter Kit for PIC18F User’s Guide

DS51852A-page 10

©

 2009 Microchip Technology Inc.

When the MicroSD bootloader starts, it initializes the capacitive touch routines and the 
OLED display. It then monitors for a MicroSD memory card insertion. When an insert 
event is detected by the bootloader, the MDD file system is initialized and the file structure 
is displayed on the OLED. Note that only folders and HEX files will be displayed.

The user can press the 

Up

 and 

Down

 buttons to select a specific file or folder. Pressing 

the 

Accept

 button when a folder is selected causes the bootloader to display the con-

tent of that specific folder on the OLED. To move one level up in the directory hierarchy, 
either press the 

Cancel

 (

Left

) button, or press the 

Accept

 button when the “..” folder 

is selected.

When a HEX file is selected and the 

Accept

 (

Right

) button is pressed, the MicroSD 

bootloader will prompt the user for a confirmation to load the file from the MicroSD 
memory card and program it to the microcontroller’s Flash memory. After this operation 
is finished, the user may choose to execute that application or to remain in the 
bootloader.

If the 

Cancel

 button is pressed in the root directory, the MicroSD bootloader terminates. 

The last application programmed into the microcontroller is then executed.

Figure 2-2 shows a typical sequence of OLED messages from the bootloader 
initialization through the loading of an application (read from top left to bottom right). 

FIGURE 2-2:

TYPICAL SEQUENCE FOR BOOTLOADER MESSAGES

2.1.1

Memory Organization

The first 40 Kbytes of Flash program memory are used by the MicroSD bootloader. 
Figure 2-3 shows the memory map of the PIC18F46J50. The application code must 
ensure that the boot area is not overwritten.

2.1.2

Remapped Vectors

Since the hardware Reset and interrupt vectors lie within the boot area, they are 
remapped through software to the beginning of the user memory space. Remapping is 
simply a branch for interrupts; users may observe an additional latency of two 
instruction cycles to handle interrupts.

Microchip

PIC18F Starter Kit

Press S1 to load the

SD Bootloader

9

Card not detected!

Please insert a valid

MicroSD card to 

continue

>>HIDDEMO
  CDC_DEMO.HEX

MSD_DEMO.HEX

>>.

..

MOUSE ~1.HEX

JOYSTI~1.HEX

The following demo
will be loaded:

Press the R button
to accept, or the
L button to cancel

CUSTOM~1.HEX

CUSTOM.HEX

Application image

has been loaded.
Press the R button to
start the application
or L button to cancel

file: CUSTOM.HEX

Use ‘up’ and ‘down’

buttons to navigate.

button to select a

Press menu button to

continue

Press the ‘accept’

file.

File is loading.

Please wait.

Mouse Demo v1.0

PIC18F Starter Kit

Press Menu to proceed