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The default software for the H2 is made up of several
interlocking shell scripts, backed up by a compiled C program
and a custom kernel. This software is all in userspace, except
for the kernel, and may be modified to develop other
applications (or improve upon the very rough sketch of an
ebook that this software represents).
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Since the H2 system uses the LCD port of the xscale to run the
display, a framebuffer must be set up in main memory and the
LCD peripheral DMA controller pointed to its base. This is
accomplished by the kernel at boot time, and consequently the
kernel must be modified to make the block of memory mapped to
/dev/fb0 the right dimensions. In the 2.6 kernel tree, fb
support for the ARM architecture is much improved and
simplified. We are using an unmodified build of the gumstix
buildroot source tree, with display support turned on and boot
command display configuration enabled (using a make
menuconfig). With this setup, we can use one kernel for all
display configurations, since we can edit the kernel command
line in the bootloader.
The Apollo model does not require the fb to be setup since the
fb is effectively built into the Apollo PCB.
Probably much about the system could be improved with some
judicious writing of kernel level drivers, but we have not had
time to do this yet.
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Display Control Utilities
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Several userspace programs are used to directly control the
display. The most important one is a compiled C program which
takes a bitmap file as input and takes care of updating the
framebufer and initiating an update. It can also take input
from stdin, so in scripted operation putput from bzcat is
usually redirected to this command.
There is also a compiled C program to scan the GPIO pins for a
button press. It can be called in either blocking or
non-blocking mode.
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A series of shell scripts are what ties all these elements
together and implements the application level
functionality.
/root/ebook_def.sh and /mmc/ebook.sh
This script controls operation in ebook mode. If /mmc/ebook.sh
exists, that script is used, if not then /root/ebook_def.sh is used.
/root/slides_def.sh and /mmc/slides.sh
This script controls operation in slidewhow mode. If /mmc/slides.sh
exists, that script is used, if not then /root/slides_def.sh is used.
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Design partially original and partially ripped off from other websites
by Holly Gates
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