[lug] voip blasters

[Paul Walmsley]

so i got a chance to tinker around with kevin's voip blaster last night at
hackingsociety.  (much gratitude to kevin for letting me take it
apart repeatedly.)

i got so caffeinated that i promptly went home and spent the next six
hours hacking on the fobbit software, trying to figure out the magic
numbers at the top of fobbit's vblast.c.  the voip blaster's on-board DSP
can DMA six ways from sunday so i thought there might be a chance that the
host software sends executable code up to the device on plugin.  sure
enough, a hand-disassembly of the init_2 string in vblast.c (start with
the 18028f) looks very very code-like.

here's the hardware specs for anyone interested.  (i think there's at
least one other chip on the thing, but i missed it somehow.)

            DSP: Analog Devices ADSP-2185M
   Flash EEPROM: SST 39VF010
Phone interface: SGS-Thomson STLC7546
  USB interface: Philips Semiconductor PDIUSBD12

all of the parts are standard & off-the-shelf.  datasheets are available
over the 'net, or i'll send my copies to you if you're interested and
can't find them.  according to the datasheets, there's no mask ROM in the
DSP or any bullshit like that - it looks totally reprogrammable. Analog
claims the DSP is "16-bit, 75 MIPS, 2.5v, 2 serial ports, host port, 80 KB
RAM".  the flash EEPROM is 128KB large.  the phone interface is basically
an A/D & D/A converter.

...

all this is pretty damn cool in my opinion.  it means that for about $20
($10 if you got your voip blaster while the getting was good), if you're
adventurous, you now have a 75 MIPS DSP development platform with audio
I/O through a phone and a headset, a USB 'device' or 'slave' interface,
and 128KB of flash.  creative labs even does you the favor of breaking
about 20 lines out to a test header on the board with silkscreened pin
names!

it's also interesting to note that MAME comes with a ADSP-2100 emulator,
so with some MAME hacking, one might even be able to simulate one's code
before uploading it!  or, run the G.723.1 codec on the host system...
hmmmm....

...

anyway, anyone interested in tinkering with this thing should drop me a
line, we can swap ideas and have a blast.  er, a voip blast.   real
hacking for me will have to wait until my voip blasters come in :-(


- Paul