• Write access for programming Intel
®
HEX formatted files into the target device’s memory
• Write access for simple text files for utility purposes
3.1.3.1
Mass Storage Device Implementation
The on-board debugger implements a highly optimized variant of the FAT12 file system that has several limitations,
partly due to the nature of FAT12 itself and optimizations made to fulfill its purpose for its embedded application.
The Curiosity Nano USB device is USB Chapter 9-compliant as a mass storage device but does not, in any way, fulfill
the expectations of a general purpose mass storage device. This behavior is intentional.
When using the Windows operating system, the on-board debugger enumerates as a Curiosity Nano USB Device
that can be found in the disk drives section of the device manager. The CURIOSITY drive appears in the file manager
and claims the next available drive letter in the system.
The CURIOSITY drive contains approximately one MB of free space, and this does not reflect the size of the
target device’s Flash in any way. When programming an Intel
®
HEX file, the binary data are encoded in ASCII with
metadata providing a large overhead, so one MB is a trivially chosen value for disk size.
It is not possible to format the CURIOSITY drive. When programming a file to the target, the filename may appear in
the disk directory listing. This is merely the operating system’s view of the directory, which has not been updated in
reality. It is not possible to read out the file contents. Removing and replugging the board will return the file system to
its original state, but the target will still contain the application that has previously been programmed.
To erase the target device, copy a text file starting with “
CMD:ERASE
” onto the disk.
By default, the CURIOSITY drive contains several read-only files for generating icons as well as reporting status and
linking to further information:
•
AUTORUN.ICO
– icon file for the Microchip logo
•
AUTORUN.INF
– system file required for Windows Explorer to show the icon file
•
KIT-INFO.HTM
– redirect to the development board website
•
KIT-INFO.TXT
– a text file containing details about the board’s debugger firmware version, board name, USB
serial number, device, and drag-and-drop support
•
STATUS.TXT
– a text file containing the programming status of the board
Info:
STATUS.TXT
is dynamically updated by the on-board debugger. The contents may be cached by
the OS and, therefore, do not reflect the correct status.
3.1.3.2
Configuration Words
Configuration Words (PIC
®
MCU Targets)
Configuration Word settings included in the project being programmed after program Flash is programmed. The
debugger will not mask out any bits in the Configuration Words when writing them, but since it uses Low-Voltage
Programming mode, it is unable to clear the LVP Configuration bit. If the incorrect clock source is selected,
for example, and the board does not boot, it is always possible to perform a bulk erase (always done before
programming) and restore the device to its default settings.
3.1.3.3
Special Commands
Several utility commands are supported by copying text files to the mass storage disk. The filename or extension is
irrelevant – the command handler reacts to content only.
Table 3-2. Special File Commands
Command Content
Description
CMD:ERASE
Executes a chip erase of the target
CMD:SEND_UART=
Sends a string of characters to the CDC UART. See “
.”
Curiosity Nano
©
2021 Microchip Technology Inc.
User Guide
50003124A-page 11
