This is a Tibbit module — part of the Tibbo Project System that allows you to build your own custom embedded device with only the components you need. Start with a Tibbo Project PCB, add Tibbits like this one, then place the built design into a Tibbo Project Box to complete your product.
Tibbit #02: Universal RS232/422/485 port with electronic mode selection.
This is a "full" serial port that can be programmed electronically to work in RS232, RS422, or RS485 mode. This Tibbit uses the Sipex SP337 universal transceiver. Mode selection is through FD/HD and 232/422-485 control lines:
|Mode ||FD/HD ||232/422-485 |
When unconnected, FD/HD defaults to HIGH, while 232/422-485 defaults to LOW. This means that the RS232 mode will be selected.
In the RS232 mode, the port has RX, TX, RTS, CTS, DTR, and DSR signals. This is the full-duplex mode.
In the RS422 mode, the port has +/-RX, +/-TX, +/-RTS, and +/-CTS signal pairs. This is the full-duplex mode.
In the RS485 mode, the port has only +/-RX and +/-TX signal pairs. This is the half-duplex mode, so you can connect +RX to +TX, and -RX to -TX. This will allow your system to communicate over a single twisted pair. Direction control is through the RTS line — the line shall be LOW for data input and HIGH for output.
For "normal" RS232/422/485 applications, this Tibbit has to be connected to the TX and RX lines of the CPU's UART (see [SER]). If you plan to use RTS/CTS flow control as well, an interrupt line must be available (see [INT]).
Combining this Tibbit with the C Tibbit #19 (DB9M connector) will create a serial port with standard pin assignment on the DB9M:
| ||RS232 ||RS422 ||RS485 |
|Pin 1 ||No connection ||TX2- (output, commonly RTS-) ||No connection |
|Pin 2 ||RX (input) ||RX- (input) ||RX- (input) |
|Pin 3 ||TX (output) ||TX+ (output) ||TX+ (output) |
|Pin 4 ||TX3 (output, commonly DTR) ||TX- (output) ||TX- (output) |
|Pin 5 ||Ground ||Ground ||Ground |
|Pin 6 ||RX3 (input, commonly DSR) ||RX+ (input) ||RX+ (input) |
|Pin 7 ||TX2 (output, commonly RTS) ||TX2+ (output, commonly RTS+) ||No connection |
|Pin 8 ||RX2 (input, commonly CTS) ||RX2+ (input, commonly CTS+) ||No connection |
|Pin 9 ||No connection ||RX2- (input, commonly CTS-) ||No connection |
Those pin assignments are the same as used on all Tibbo devices with a universal serial port (e.g. DS1102).
You also can combine this RS232/RS422/RS485 Tibbit with #20 (nine terminal blocks).
There are eight LEDs. Red LEDs are connected to the TX, RTS, DTR, FD/HD, and 232/422-485 lines. Green LEDs are for RX, CTS and DSR. All of these LEDs are buffered (with logic gates) and light up for the LOW state of control lines.
- Form: M2S
- Power: 5V; consumes 40mA
- Special lines: [SER], [INT]
- Mates with: #19, #20
- Similar to: #01, #05
M2S Tibbit Modules Overview M2S Tibbits are double-width modules occupying two standard M sockets on a Tibbo Project PCB (i.e. TPP2 or TPP3). Their footprint is roughly 14 × 14 "squares" (one "square" is 2.54 × 2.54 mm). The M2S modules are 12.5mm high.
M2 modules have four groups of 6 pins arranged into two rows:
Pins 14-17 and 20-23 are control lines A-H.
Pins 2-5 and 8-11 are I/O lines.
Pins 12 and 24 are the GROUND and +5V power pins.
Pins 1 and 13 are for the optional +15V and -15V voltages needed only by few Tibbits. A special power supply Tibbit (#12) generates ±15V from the main 5V power.
Pins 6, 7, 18 and 19 are unused and should be left unconnected.
Notice that each pin row has a "missing pin" in this middle. This separates a row into two groups of 6 pins.