The Department of Computer Science and Software Engineering at the
University of Melbourne has designed
two versions of a general-purpose single-board computer, either of which can
be used as a development platform for network tools such as routers, network or
video security monitors, autonomous robots and as Real-Time-Operating-Systems
teaching and research tools. These new designs update our previous workhorse
platform which used the Motorola 68k and derivatives.
Our development-boards are powered by a
MPC860 Power PC
embedded-processor comprising three major components: Power PC core, System
Interface Unit (SIU, the internal bus controller) and a PowerQUICC
The smaller version of the board (4.0 inches by 5.0 inches) contains the
o glue logic provided by a single M4-192/96 programmable logic chip
o one communications expansion port (serial, ethernet, MII/FEC, TDM)
o DRAM memory using a 72-pin SIMM (maxm 32Mb)
o boot ROM/Flash chip (256Kbyte Ð 1Mbyte)
o one 10Mbs ethernet 10BaseT interface
o one low-speed RS232 serial interface
o one low-speed TTL serial interface
o CompactFlash Card (4 - 45Mb)
o LCD module connector port
The Baby PPC was designed for future use in small projects, including for
our F-180 series robots as used in the Robocup
The larger development-board (double eurocard size) includes:
o three Vantis programmable logic chips
o DRAM 72-pin SIMM (32Mb) or 168-pin DIMM (256Mb)
o single-height 3.3-volt or 5-volt PCMCIA socket
o boot ROM/Flash chip (256Kbyte - 1Mbyte)
o CompactFlash Card (4 - 45Mb)
o three 10Mbs ethernet interfaces (2 x AUI/3 x 10BaseT)
o dual 12Mbs/1.5Mbs Universal Serial Bus (USB) sockets
o optional single RS422/LocalTalk via header connector
o 1.152Mbs IrDA infra-red communications port
o single 33MHz, 32-bit, 3.3-volt PCI slot
o dual low-speed RS232 interfaces
o dual TDM interfaces for T1/E1 & ISDN
o general-purpose 8-bit I/O expansion port
o DTMF and musical tone encoder
o DTMF tone decoder
o quad low speed A/D converter
o single low speed D/A converter
o dual medium-speed D/A converter
o stereo high-current audio amplifiers
o miniature speaker and headphone socket for audio
In addition to the varions ethernet, serial and comms expansion ports
listed above, the boards also provide headers for access to the MPC860
I2C, SPI and
JTAG/TAP debug ports and both have general-purpose daughter-board expansion
interfaces for off-board memory or video processing.
on the left shows a small digital camera interface that connects to
the bus expansion slot on the bottom of the
baby PPC (the connector is underneath the board).
The board buffers a complete digital frame, making the 16-bit pixel data
available to the processor in memory space.
Our development environment of choice is NetBSD which includes the 'pkgsrc' environment that allows you to do
to create the appropriate cross assembler, C compiler and loader
for PowerPC chips. Simple.
The current Boot Monitor PROM (v1.1) allows setting of serial EEPROM
parameters, including preferred console port and CPU speeds, boot file
name (from the compact flash), auto-boot or straight to monitor at
startup, hostname and miscellaneous others. The flash card DOS file
system can be inspected with the 'ls', 'cd' and 'more' commands.
The MPC860 Power PC chip has several family members. The development board
currently uses the MPC860SAR, a chip tailored specifically for use with ATM.
The major drawback with this chip is that the on-board DSP micro-code has been
removed to make room for the ATM micro-code. In all other respects this is a
vanilla MPC860. The MPC860 series comes packaged as a Plastic Ball Grid Array.
Ball Grid Arrays
A Ball Grid Array (BGA) is essentially a small printed circuit board with the
electronics encapsulated into a plastic package on the top of the board. The
bottom of the board has a set of round pads onto which are mounted low-melting-
point solder balls. The BGA is attached to a PCB by placing it over the
corresponding PCB pads and heating until the solder melts.
Although doing this properly requires expensive and accurate placement
equipment, you can actually achieve useful prototyping results using garden
variety kitchen equipment and a typical surface mount rework hot-air gun.
The surface tension of the molten solder will actually centre the chip
if it is placed up to 50% off the pads (Motorola Application Note
The bottom of the chip is shown at left, there are 357 pins in a 19x19
array (4 missing corners). The actual size is 1 square inch.
BGA Mounting: Doing It Yourself
Here's a brief 10 step description ...
1. Obtain an ancient electric frying pan.
2. Cut off the raised sides with an angle grinder.
3. Mount a solid piece of aluminium on the hotplate.
4. Insert screws from the bottom to match the PCB holes.
5. Cut 0.8mm thick aluminium strips to raise the PCB off the aluminium plate
(don't want the plate to be an effective heatsink).
6. Cut and drill ~5mm thick aluminium strips to to tie down the PCB edges
and prevent the board from warping.
7. Clean pads, add appropriate SMD rework flux, place BGA as carefully
as you can. It helps to have accurate printed artwork.
8. Heat the aluminium plate to around 100 degrees C (the PCB will be at ~90 deg C).
9. Set matching square-nozzle re-work heat gun for 230 deg C for around 3
minutes (temp. and time subject to experimentation).
10. Turn off and wait until everything cools down again.
This requires appropriate amounts of daring-do and patience.
Thanks to Bryan Cook for the concept and demonstration.
It's way harder than it should be to source electronic components
in Australia, particularly when you need shorter than 26 weeks
delivery time and quantities of less than hundreds or thousands.
For that reason we'd like to mention the fast and helpful people
that we deal with. We don't have any commercial arrangements with any
of the following, other than as satisfied paying customers.
Entech Printed Circuits