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MoBoStamp-pe BS2pe Motherboard (#28300)
General Description
The MoBoStamp-pe provides a compact, professional-grade platform for BASIC Stamp applications. With
the MoBoStamp-pe and the assortment of available daughterboards, you will be able to integrate and
package one-off or multiple application systems with ease. The onboard AVR coprocessors permit the
offloading of compute-intensive and background tasks from the BASIC Stamp, yielding a high
performance level, while retaining the BASIC Stamp’s ease of programming. They come preprogrammed
for digital I/O, analog input, pulse-width-modulated output, and frequency counting. Each coprocessor
interfaces to both the BASIC Stamp and one daughterboard each and may be reprogrammed by the user.
Potential uses include background serial I/O, floating point processing, and background servo pulsing.
Before using your MoBoStamp-pe, please read and understand this entire document.
Features
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Compact size: designed to fit available packaging.
BS2pe BASIC Stamp chip for high performance with low current consumption.
32K x 8 EEPROM for program and data storage.
Built-in USB interface, capable of powering the entire board.
Two sockets for plug-compatible daughterboards, enabling the easy integration of sensors and
interface options.
Two user-programmable Atmel AVR coprocessors, preprogrammed for digital I/O, PWM output,
analog input, and frequency measurement.
Multi-mode power sourcing: board can run from USB or external power.
Multiple Vdd levels: 3.3V and 5V, jumper selectable.
User-programmable multi-color LED for status indication.
Programming header for future interface to an SX-KEY. This will allow programming the SX chip
directly.
Application Ideas
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Robotics
Remote Sensing
Data Acquisition
Industrial Control
Desktop Appliances
What’s Included
1 ea. MoBoStamp-pe Motherboard, preconfigured with:
4 ea. 3/16” dia. x 5/16” Threaded Standoffs
8 ea. 4-40 x 3/16” Panhead Machine Screws
3 ea. 2mm Jumpers
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Interface Connections and Jumpers
Power Source Vdd Select Daughtercard Coprocessor SX Programming
Jumper
Jumper Socket "B"
"B"
Header
External
Power
Vdd "On" LED
USB
Connector
Reset
Button
Bicolor
LED
RxD to AVR A1
Jumper
External Power Connector
Daughtercard
Socket "A"
Coprocessor
"A"
The external power connector enables the connection of a filtered, unregulated 6-9VDC power supply to
power the motherboard. The plug and cable for this connector may be obtained separately from DigiKey,
using the part numbers given under “Specifications” near the end of this document. Power applied here
supplies both the onboard 5V regulator and the Vin connection to Daughterboard Socket “A”.
Vdd “On” LED
This LED comes on when the board’s Vdd is active. When the board is powered externally, this will occur
whenever external power is applied. When the board is powered from the USB port, the LED will come on
once the board has been connected to a USB port and the onboard USB chip enumerated by the PC.
For applications (such as light-sensing) where such a light source is undesirable, or for situations
requiring minimum current draw, there is a “bow-tie” trace on the bottom of the board (under the
external power connector) which can be cut to disable the LED.
USB Connector
The USB connector is the mini-B type. Compatible “A-to-mini-B” cables may be obtained at most local
computer stores or from Parallax as part number 805-0006.
Power Source Jumper
The power source jumper can be placed to select either external or USB power. When external power is
selected (upper position, marked
EXT),
the onboard regulator provides 5V to the rest of the board from
Vin. Vin can come from either the external power connector or a daughterboard plugged into
Daughterboard Socket “A”. The USB chip, however, will continue to be powered by the host PC through
the USB cable.
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When USB power is selected (lower position, marked
USB),
the host PC provides 5V to the rest of the
board from the USB cable.
Note:
The USB “5V” supply can range anywhere from 4V to 5V.
When an
accurate supply voltage is critical (e.g. for analog applications), it’s best either to use an external supply
or, if all circuitry can run from 3.3V, to select a Vdd of 3.3V.
Vdd Select Jumper
The Vdd select jumper allows the BASIC Stamp, the EEPROM, and both AVR coprocessors to run from
either 3.3V or 5V. By selecting 5V (lower position, marked
5V),
Vdd is provided by the power source
jumper, without further regulation.
By selecting 3.3V (upper position, marked
3.3V),
the onboard 3.3V regulator supplies these chips, as well
as the “Vdd” pin on each daughterboard connector. In this position, the “5V” receptacle on each
daughterboard connector continues to receive 5 volts.
RxD to AVR A1 Jumper
This jumper allows the incoming serial data from the USB interface to be connected to one of the AVR
coprocessor pins. This will permit a properly programmed AVR to receive serial data in the background,
relieving the BASIC Stamp of the task.
SX Programming Header
This six-pin header includes all the signals (plus RST) required to reprogram the SX with something other
than the BS2pe interpreter. This function will be available via an adapter that the Parallax SX Key plugs
into.
Important:
Overwriting the BS2pe firmware is permanent. It is not possible to revert to BASIC
Stamp operation once this has been done.
For normal operation, this header should always be configured with a jumper in the lower right-hand
corner, thus:
Reset Button
The tiny reset button, when pressed, will reset the BASIC Stamp chip and both AVR coprocessors. It’s
designed more to be used in conjunction with a paperclip and a pinhole enclosure opening than with a
finger; hence, its diminutive size. During debugging, resetting the board via the debug screen’s DTR
button will likely be easier.
Bicolor LED
This red/green LED is illuminated by pulling BASIC Stamp port P13 low for red or P14 low for green.
Pulling both low simultaneously will show, at a distance, as amber.
Daughterboard Sockets
The daughterboard sockets receive the specially-designed daughterboards which, in conjunction with the
onboard AVR coprocessors, perform sensing, interfacing, and other functions. They are labeled “A” and
“B”.
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The daughterboards plug in parallel to the motherboard and will typically have connectors facing the
ends of the motherboard. The daughterboard sockets are identical, with one exception: the “A” socket
carries the Vin signal, while the “B” socket does not. This permits a daughterboard plugged into the “A”
socket to power the whole system. That way, daughterboards can be designed, for example, with 24V-
input DC-DC converters for industrial systems, or simple wall-transformer inputs for hobby systems. The
Parallax PWR-I/O-DB card (part #28301) is an example of the latter.
Important:
Never insert jumper wires into the daughterboard sockets. Unlike 0.1” header sockets,
these are not big enough to receive most jumper wires without damage.
The “A” daughterboard is sometimes referred to as the “Interface” daughterboard, since it is frequently
used to interface to the outside world, with its connectors on the same end of the motherboard as the
USB connector. Likewise, the “B” daughterboard is often called the “Sensor” daughterboard, since that’s
the socket where sensors are more likely to be plugged in. In reality, these names are arbitrary, since the
capabilities of the two sockets are virtually identical.
In addition to the Vin line for socket “A”, each daughterboard socket includes +5V, Vdd, Gnd, and eight
signal lines. It is convenient to think of the signal lines in pairs. Their functions can be described as
follows:
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Common pulled-up pair:
These lines connect to both sockets and also to BASIC Stamp ports
P2 and P3. They are pulled up to Vdd via 4.7K pull-ups. They can be used for daughterboard-to-
daughterboard communication, without BASIC Stamp intervention. They can also be used with
open collector drivers as poll inputs to the BASIC Stamp or as actual interrupts to a raw SX
system.
Individual pulled-up pair:
These lines connect ports P8 and P9 to socket “A” and P0 and P1 to
socket “B”. They are pulled up to Vdd via 4.7K pull-ups. These ports can be used with the BS2pe
firmware as an I2C interface. Daughterboards with I2C peripherals will use these lines as SDA
and SCL.
AVR/BASIC Stamp shared pair:
Two lines to each daughterboard connect to both the BASIC
Stamp and to the daughterboard’s associated AVR coprocessor. These lines are not pulled up.
Socket “A” receives P11/A2 and P12/A3. (A2 and A3 are pin designators for coprocessor “A”, as
shown below.) Socket “B” receives P7/B2 and P5/B3. A2, A3, B2, and B3, can be programmed as
PWM outputs from the AVR chips.
AVR exclusive pair:
Two lines to each daughterboard connect exclusively to its AVR
coprocessor. These are A0 and A1 for socket “A” and B0 and B1 for socket “B”. These pins can
be programmed as analog inputs.
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The foregoing description is summarized in the following schematic fragment:
Coprocessors
The two AVR coprocessors interface to the daughterboards and to the BASIC Stamp as shown above. P6
and P10 are reserved for BASIC Stamp/AVR communication. These lines are pulled up to Vdd, so that
open-collector comms (e.g. OWIN and OWOUT) may be utilized. The actual interface details will depend
on the AVR firmware. See the GPIO-3 document for the firmware that comes preinstalled on the
motherboard.
Getting Started
Before connecting your MoBoStamp to a PC, you should download and install the FTDI drivers necessary
to operate the USB interface. These can be obtained, along with installation instructions, here:
http://www.parallax.com/html_pages/downloads/software/ftdi_drivers.asp
For programming the BASIC Stamp, you will need the Parallax BASIC Stamp Editor software, available for
download here:
http://www.parallax.com/html_pages/downloads/software/software_basic_stamp.asp
Finally, to use the general-purpose I/O firmware pre-installed in the AVR coprocessors, download the
GPIO user’s guide here:
http://www.parallax.com/detail.asp?product_id=28300
Once these tasks have been completed, make sure your MoBoStamp is jumpered for USB power, and
plug it into your PC. You should hear a “boo-beep” signal from the PC, indicating that the device has
been recognized, and the green Vdd “on” LED should light. You are now ready to start programming.
© Parallax, Inc. • MoBoStamp-pe (2006.09.13)
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