External Serial Port
When I added an external connector for the serial port to my -R1, I used a connector that matched a TTL-USB cable I already had.
For the serial port connector on my -R3, I decided to use a three conductor audio plug and jack (3.5mm, 1/8 inch).
I already had on hand a TTL-232R-3V3-WE adapter cable for another project.
The signal assignment page from the technical reference sheet for that adapter:
For the pin-out on the cable, I decided to do the same as on the TTL-232R-3V3-AJ cable:
This only required cutting back the three unused conductors (CTS, RTS, +5 volt) close enough to the
end of the outer jacket so they would not get into trouble.
The new cable plug parts, ready for the hot iron:
The connections will be:
| Cable | Connector | J6 Pin |
|---|---|---|
| TXd | tip | RXd |
| RXd | ring | TXd |
| Gnd | sleeve | Gnd |
On the back of the O!Play are the three composite video and audio conntectors with a nice blank spot
for a fourth connector.
First step is to punch a hole in the rear shield to mount the jack aligned with the existing connectors:
At this point, transfer the center of the hole just punched in the shield to the rear panel of the case.
On that center, punch a larger hole, large enough to clear the outer barrel of the audio plug.
No picture. This is just a clearance hole for the barrel so that the plug will fully seat into the jack.
The matching, 3-wire jack that will be mounted:
Next step is to make an internal, serial port cable.
The header connector from a three or four wire audio cable for an internal CDrom player is the proper size.
This time, I used a three wire header connector from an old CPU cooler fan; also a matching size.
The internal cable:
Then mount the 3-wire jack with attached internal cable to the rear shield:
Now remount the rear shield and replace its mounting screw:
Being very careful not to connect to the O!Play's 3.3 volt pin, plug the internal cable into the serial port header.
Note: if you are "off by one" placing this connector on the pins, you will ground out the 3.3 volt power supply.
The modified -R3 re-assembled:
Phooey! Can't find my old Rubber Ducks, so ordered a pair of these things:
http://www.l-com.com/item.aspx?id=22372
And a pair of magnetic base stands with 5 foot cables attached:
http://www.l-com.com/productFamily.aspx?id=6346&cmp=MI
