VS1000
7
FIRMWARE OPERATION
7.4 Default Firmware Features
7.4.1 USB Mass Storage and Audio Device
When USB cable insertion is detected by the firmware, playing of the current file is stopped
and USB handling code is started. The internal clock is configured to 4.0× 12 MHz = 48 MHz,
the analog power is configured to 3.6 V, the USB peripheral is initialized, and the USB pull-up
resistor is enabled.
If GPIO0_6 has a pull-up resistor, VS1000 appears as an USB Audio Device. If GPIO0_6 has
a pull-down resistor, VS1000 appears as an USB Mass Storage Device.
If during power-on the NAND FLASH contained a valid boot sector, the NAND FLASH disk
will be used with the mass storage device. The NAND FLASH disk requires a filesystem-level
formatting before it can be used. If NFCE had a pull-down instead of pull-up, or if a valid boot
sector was not found, a RAM disk is used instead.
The RAM disk is preformatted and can be used immediately, but it does not retain its contents
between USB detachment and insertion. The RAM disk is only intended for loading software
through USB. You can copy a file VS1000_B.RUN to RAM disk and it will be automatically
run when you disconnect the USB cable. This mechanism can be used to program the NAND
FLASH boot sector (perhaps containing custom boot code), and also for programming a SPI
EEPROM in case NAND FLASH is not used in the application.
7.4.2 Default Player Application
When the USB cable is detached, the contents of the disk is checked. If the disk seems to
contain a FAT16 or FAT32 filesystem, a cleanup of unused sectors is performed. The cleanup
makes the disk perform faster the next time something is written on it. If a full disk has been
formatted or emptied, this cleanup can take considerable time, even 30 seconds or more. After
the cleanup is finished the player starts to play files.
Note: normally Windows formats smaller than about 16 MB disks as FAT12. The player has only
partial support for FAT12 disks: no cleanup is performed, subdirectories are not allowed, and
files are assumed not to be fragmented. If disks as small as or smaller than this are required, it
is possible to format them as FAT16 with the following command.
The default player application only decodes Ogg Vorbis files, but it can be extended to allow
some simple codecs, like a WAV decoder.
In addition to the power button, 5 keys are connected to GPIO0_[4:0] so that they connect
a 10 kΩ pull-up to the I/O when the button is pressed, and 100 kΩ pull-downs keep the lines
low otherwise. The resistors are needed because these lines are also used for NAND FLASH
communication. The keys are read approximately 16 times per second.
The key control can be changed by replacing the default key mapping table. The default user
interface uses six buttons.
Version: 1.4, 2011-10-06
19
ETC [ ETC ]
