The SIM_1A is
available as a general purpose embedded PIC project board. With a bit
of programming it can be a very powerful little controller of only
64mm x 39mm x 22mm.
It includes a
surface mount PIC16F876A with a 20MHz crystal as standard. Most of
the I/O connections are via a 40-pin box header which accepts an IDC
plug and ribbon cable. We can also supply it with a dual-row
right-angle or straight header pin strip for circuit board mounting.
The serial port, power and a few I/O connect via miniature screw terminals.
The SIM_1A was
designed recently to be a networked I/O moduleas part of our PMBACS
control system. Multiple SIM_1A modules can connect via a single
CAT-5 or security cable to a master controller. The SIM_1A provides
local I/O connections, some preprocessing and then transfers data to
the master. The screw terminal connections are for connecting field
wiring that can be run some distance from the SIM_1A without
additional protection. The 40-way header is intended for local I/O
that does not run far from the board; typically switches, LEDs, light
sensor, temperature sensor etc.
If you want to
interconnect SIM_1A boards We can provide a starting point for
networking and a simple protocol and the rest is up to you. We're not
currently providing full network support software but may do so at a
later date. We are currently developing an upgrade to our existing
The SIM_1A can
be powered from 12V DC supplied via the screw terminals. This
configuration allows a number of SIM_1A boards to be connected
together on a single cable forming a simple network. The boards are
powered and communicate over the one cable. The maximum length
possible depends on the type of cable and the loading at each board.
The eight low
level digital outputs are provided by an on-board 74HC595 serial to
parallel latch. These can be used to directly drive LEDs. A simple
software routine is required to update the outputs.
The same CPU
lines that drive the on-board 74HC595 are available via the 40-way
header. This allows the number of outputs to be increased off-board
by adding additional 74HC595 chips. Additional inputs can be added
using a similar parallel to serial interface chip.
current outputs can handle an amp or so each. The power supply and
connections must be rated to handle the current. The outputs are
mosfet switched to 0V (ground). These outputs can be used to switch
loads up to an amp or so at 12V. They are suitable for controlling
door locks, lamps and alarm sirens.
"low-level" we mean 0 to 5V logic level signals. All I/O
lines within the 40-way header include on-board series resistance to
provide some protection of the on-board circuitry. This also allows
the outputs to directly drive LEDs without an external resistance.
serial port is available at the screw terminals. These lines are
protected on-board by an R-CZ-R arrangement and can be run some
distance without additional protection. The serial RX and TX lines
are at 0 to 5V levels. For connection to a PC serial port a level
converter such as a ST232 or MAX232 will be required.
A 5-pin single
row header allows simple In-Circuit-Serial-Programming. A 5-pin Molex
single row 2.54mm pitch plug is required to connect for programming.
The header provides connection to ground, +5V, data, mclr, and clock
(- + D M C) in that order. Power should be applied to the board for
programming. It's unlikely the ICSP programmer will be able to power
the board during programming.
The I/O have
been labeled A, B, C, D and Z: