| The PinStem modules are piggy backed to form
the PinStem bulk (see example on the right). Every pin can be an input, an output or disconnected from the
process by either cutting pins or adding extra cut pin-array and hence denying connection (note that
in this case through connectivity is also denied). |
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| Modules are framed to protect the pins, they
can be removed from the frame if corner screws are removed. Each
module height division is 4mm whether framed or not. Frames have holes on each
corner 40mm apart for M3 bolts that clamp the modules together into a
rugged structure. |
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| Standard 26 gauge wire can be forced into the
socket as shown on the right. If standard ribbon cable is used with
stranded wires, they need to be twisted together tightly packed and
pre-tinned before attempting to force them into the pin socket. Solid wires
26 gauge need no special attention. Frames when clamped
together using bolts will provide an adequate strain relief for the
ribbon cable or other wiring. I.e it takes force to pull
the cable out. |
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Single pin for all information
exchange (compin)
PinStem uses a single (reserved) pin for simplex information exchange by default.
We refer to this pin as the compin.
Information exchange protocol in this case is TTL USART. This pin is
used to upload programming code, and for standard I/O used by e.g. the C
printf instruction. Due to the
simplex nature of the conduit a multidrop operation is possible, meaning many modules
may simultaneously be using this pin either to receive or emit data.
While emitting the pin is in an output state, at all other times it is a
listener or in an receive mode. By connecting the RX and TX pins
together with a 1Kohm resistor, a conventional TTL USART can read and
write data to the stack through the RX line at 460800 baud. Some
processors provide extra com channels at much higher rates. |
WiFi 802.11
Add-on Module
The wifi add-on utilizes the "compin". Since the
RX and TX are joined, all data sent from a remote computer through this wifi
socket connection gets echoed back to the input buffers of that same
computer. These add-on
modules can be set as a hot spots or stations on a wifi 802.11 network. When set
as a station the user will have access to many different PinStems from the
external program.
More
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Multiple processing modules on
the same stem
Each processor on the PinStem can be addressed and programmed individually
through a boot loader. Uploading of new programs takes place through the
default "compin". The inter processor communication is left up to the user
through any of the remaining 32 pins. To break application program and
activate boot loader to load a new program the reset button can be
pressed. Note that all processors connected to the reset conduit pin
(through pin) will exit their respective application, the units run the boot loader and expect
either an instruction to run an application or load a new one. |
Xmega processing module
(see more info)
The xmega is the latest in a line of
very successful 8 bit AVR microcontrollers from Atmel. Xmega is the next generation
up from the ATmega (arduino). Xmega sports an
instrumentation grade signal conditioner with variable gains to 64v/v, a
2Ms/s 12bit A/D and an I/O subsystem.
|
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| The development system |
| The PinStem can accommodate many microprocessors having myriad of
different peripherals. Each processor requires special attention and
comes with a pin map (outlining the function of each pin). A common denominator
for all PinStem processing modules is the programming package
and the single pin "compin" information exchange protocol. The kit is
furnished with the GNU compiler for the C-language. There is no IDE
integrated development environment, IDE requires extra learning,
instead a simplified directory structure allowing the user to compile
upload and test without any need to set up or install. This makes the
software bundle light, flexible and mobile. There is however nothing
that prohibits the use of IDE. Note that Python 2.7 should be installed
on the computer, python is free. Go to
www.python.org |
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| This example uses one of the ATMEL processors
8bit AVR xmega, click on examples. Below: the basic development package
contains 3 sub folders "basic float template" compiles using a floating
point library, this allows the user to apply floating point math in the
code. The IMU folder contains special library for accessing the on board
IMU. To add a new project it is best to make a copy of one of these
folders into the same root directory, and modify the code. |
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| Blinking LED is one of the simplest ways to get
started. Click on blink LED |
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| All example folders contain six basic files: |
- make_code: builds a file that the AVR Xmega processor can run
- load_code: uploads the code to the Xmega processor and
instructs the Xmega to run it.
- dialog: Terminal or console enables direct communication with the hardware stack so
the user can input and output data from the program.
- system: this file dictates which processor on the hardware
stem
should receive the code, what gateway the code must go through to
get to the PinStem wifi or USB. Timeout dictates for how long the code
may run, if omitted it runs indefinitely. Bin selects either binary
or ASCII exchange for the dialog terminal program. Log sets to which file the
dialog exchange data is stored. The double slash makes the line
a comment which the executing program then ignores.
- source.c: contains the C-language source code, must always have
the same name "source".
- library.s: is a an assembler source, the user can write own
efficient assembler
modules to plug into the C source code.
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| The LED blink source code |
 |
For reference click
on this link to see the PinStem Xmega I/O map.
This program runs on the Xmega processor.
Unlike it's popular predecessor ATmega, the Xmega processor allows
variable clock source. Internal and external, clock controls are found
in the sys_clock.h file. The instruction set is similar to the ATmega
(arduino),
porting code from the old chip is not a big problem. Here is a good chance to
upgrade to Xmega. |
Try your own code
For starters just change the time interval in the above source code to
say 12500 cycles or double 6250 cycles. Click on make_code and
then click on load_code, observe the LED slow down and your first
PinStem program is working. |
