DDB9T Hardware
By Denman Software
Dual RS232 adapter for Micro Controller Development
Dual DB9 Terminator (DDB9T)
DDB9T is a flexible adapter for interfacing Logic level serial data with RS-232 level devices.
It is available in a variety of flavours to suit your needs.
All versions supply 2 channels of bi-directional RS-232 conversion.
The simple version provides a 3-wire interface using Transmit, Receive and Ground.
The fully populated version provides a 5 wire interface that supports
hardware flow control by adding Request to Send and Clear to Send signals on each channel.
The connectors are DB9 male connectors configured in the same manner as a standard rs-232 port on most Computers. A null modem cable can be used to connect the DDB9T device to a PC.
Common Configurations:
Top: 2 channel 5 wire RS-232 powered by external supply.
Middle: 2 channel 3 wire RS-232 powered by external supply.
Bottom: 2 channel 3 wire RS-232 powered by user circuit.
On Board Power supply:
Power supply options include:
- Circuit power supplied by user over the 10 pin ribbon cable JP1
- Power supplied by external 9 volt power source on JP2 (approx. 20 ma)
- Power supplied by external 9 volt power source on JP2.
This can be used to supply regulated power (up to 50ma)
to the user circuit over the 10 pin ribbon cable JP1.
- Power supplied by external 9 volt power source on JP2.
Heavy duty regulator option can be used to supply regulated power
(up to 250ma with appropriate heatsink)
to the user circuit over the 10 pin ribbon cable JP1.
The optional regulated power supply uses an adjustable regulator (National LM317) This can be used to provide other voltages than the standard 5.0V if needed.
The resistors in use for a 5.1V supply are 243(upper) and 750(lower). A quick way to change to a 3.2V supply is to piggy back a second 750 ohm resitor onto the first creating a 243 and 375 ohm set resulting in 3.2V
Note: The Tab of a TO-220 style LM317 is not Ground as with the more common 7805 type of regulators. If you are supplying your circuit from this power supply and are installing a heatsink you must ensure that the heatsink is isolated from the rest of the circuit.
Connector Definitions:
| J1,J2 | DB9 Male connectors |
| Pin # | Usage | In/Out | Notes |
| 1 | not used | | |
| 2 | Recieve Data | In | |
| 3 | Transmit Data | Out | |
| 4 | DTR | connected to DSR | |
| 5 | Signal Ground | | |
| 6 | DSR | connected to DTR | |
| 7 | Request to Send | Out | 5 Wire Option |
| 8 | Clear to Send | In | 5 Wire Option |
| 9 | not used | | |
|
|
| JP1 | 10 Pin ribbon cable header |
| Pin # | Usage | In/Out | Notes |
| 1 | Tx Data to J1(3) | In | |
| 2 | Tx Data to J2(3) | In | |
| 3 | Rx Data from J1(2) | Out | |
| 4 | Rx Data from J2(2) | Out | |
| 5 | RTS to J1(7) | In | 5 Wire Option |
| 6 | RTS to J2(7) | In | 5 Wire Option |
| 7 | CTS from J1(8) | Out | 5 Wire Option |
| 8 | CTS from J2(8) | Out | 5 Wire Option |
| 9 | Ground | In/Out | |
| 10 | Vcc | In/Out | JP3 pins 2,3 jumpered |
|
| JP3 | Power selection jumpers |
| Option | Jumper | Notes |
| User circuit supplies power | 2,3 | |
| External power through onboard regulator | 1,2 | |
External power through onboard regulator
also supplying user circuit |
1,2,3 | Use with Caution |
|
|
| JP2 | 3 Pin Power input header |
| Pin # | Usage | Notes |
| 1 | Ground | |
| 2 | Vin | 9VDC |
| 3 | Ground | |
|
Specifications:
| description | typical | min | max | units |
| length | 3.0(77) | | | in(mm) |
| width | 1.7(43) | | | in(mm) |
| height | 0.7(17) | | | in(mm) |
| weight | ?(?) | | | oz(gram) |
| External Power | 9 | 7.5 | 10.5 | Vdc |
| | 20 | 10 | 50 | ma |
|
|
