Note: This version has been replaced with the newer version 3.2.
RS-232: This module is used to control external components via the I²C bus using simple command sequences sent and received via an RS-232 port from an application running on a PC (sample Visual Basic application with source code is included), PDA, or other platform. The on-board MAX-232 level shifter insures there will be no signal level problems and allows for maximum cable length.
I²C Bus Master: The RS-232 / I²C-Adapter acts as an I²C master, and can perform the most frequently used read/write operations via the bus without the need for the application software to handle the I²C protocol. When the application sends one of the "macro command sequences", the adapter takes care of generating the start condition, transmitting the address plus the R/W bit, transmitting/receiving data bytes plus setting/reading the acknowledge bit, and finally generating the stop condition. All of this is transparent to the application software.
I²C low-level: To ensure compatibility, the adapter also allows the application software to directly "talk" to the I²C bus in order to allow communications with I²C devices that require non-standard sequences, using "low-level commands".
I²C Monitor: In its Monitor mode, the module acts as an I²C "spy", i.e. it passively monitors an I²C bus, and sends the byte data transferred via the bus together with the information, if there was an acknowledge, or not via RS-232. An internal 32-byte FIFO buffer, together with an 115.2 kBaud RS-232 rate allows for I²C bus rates of up to 100 kBit/s to be monitored.
Relay Output: In addition, the RS-232 / I²C-Adapter comes with a reed relay which can be controlled by dedicated commands. This allows the application software to initialize various devices via the I²C bus before finally turning on the power supply for other components, for example. Besides this, the relay may also be used as a general-purpose isolated output.
General Purpose I/O: There are also four non-isolated outputs, and eight non-isolated inputs that can be set/read by specific adapter commands. The inputs also clock eight individual 16-bit counters that may be read/reset by designated adapter commands.
Reliable WDT: As an additional option, a timer may be activated that resets the I²C-Adapter when new commands are not received within the specified time-out period.
Status Indicators: Thee LEDs are used to indicate the status of the RS-232/I²C-Adapter, the activities on the I²C bus, and the RS-232 lines.
The RS-232/I²C-Adapter is based upon a Ubicom/Parallax SX-28 microcontroller, clocked at 50 MHz. Single, pre-programmed chips are available for customers who want to integrate the RS-232/I²C-Adapter's functionality into their own hardware design (see below).
All modules are shipped with a CD-ROM containing the documentation, schematics, assembly instructions, and the sample VB application project.
This is a companion board for the RS-232/I²C-Adapter which can piggy-back via two 14-pin header sockets.
DB-9 Connector: An on-board standard SUB-D 9 connector is provided to directly connect the RS-232/I²C-Adapter's serial port to a COM port.
Isolated Inputs: It also contains eight PC849 opto-isolators to convert the RS-232/I²C-Adapter's input lines into isolated inputs.
Relay Outputs: Four reed relays are included to isolated the 4 TTL outputs from the RS-232/I²C-Adapter. The RS-232/I²C-Adapter relay output is fed-through to two separate connectors.
Analog I/O: In addition, the board comes with a Philips PCF8591 chip which extends the I/O capabilities of the RS-232/I²C-Adapter to four 8-bit analog inputs, and one 8-bit analog output.
Power : An on-board DC/DC converter enables this module to accept any DC supply voltage from 8V to 38 V, un-regulated. The DC/DC converter output is available to supply other components that are connected to the Parallel/Analog I/O Board.
All modules are shipped with a CD-ROM containing the documentation, schematics, and assembly instructions.
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<A HREF="http://massmind.org/techref/scenix/rsi2o3i2c/index.htm"> RS-232 / I²C-Adapter & Parallel I/O Module</A>
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