ROV controller?

DavidNyman

I'm planning to build an ROV for use at the local lake. I've done quite a bit of reading on the subject and think I'm about ready to begin.
I'd like to control the system with two Basic Stamps, namely the BS2 or BS2sx. One stamp will be topside to drive an LCD and accept joystick controls. The second stamp will be subsea and needs to be capable of receiving data and sending data via the tether to the topside stamp. I've found a circuit that allows two stamps to communicate via two I/O pins on each stamp, there's not much range though. I'd like to be able to reliably communicate as mentioned over a 150' tether.
I'll be using a live video feed on a dedicated coax so the BS2 won't be handling any of the video duties.
I've read a little about the Maxim Max232CPE chip but am not sure if this will work for me.
Can anyone suggest a method and possibly provide a schematic to accomplish all this?

Even sweeter would be to do the above over a fiber optic cable!

I appologize if this has been covered elsewhere. If it has, I couldn't find it.

Thanks!

DavidNyman

Would it be possible to use a Max232CPE at each stamp location then just connect the TX/RX of the Max232 chips together through my tether?

skylight

As the length is over 50ft you may need to use special low capacitance cable as specified by the standard

http://en.wikipedia.org/wiki/RS-232

Duane Degn

I believe RS-485 can be used at greater distances than RS-232.

There are some articles about using RS-485 written by JonnyMac in past Nuts & Volts. (See post #3 of my index(see signature for my index).)

DavidNyman

Thanks to Duane for the articles by JonnyMac post. Now I've got a working RS-485 network for my ROV.

Would anyone be willing to write some simple code for me to run this network?
My skills at writing code are "entry level" at best.
I'd be willing to pay a little for your time.

Here's what I would like:
As mentioned above, I have two BS2 stamps linked with 75176 RS-485 transceiver chips at each end of a 100 foot section of cat5 cable.
I'd like to be able to control two thrusters with a joystick . Currently the joystick ties to an LTC1298 A/D converter and gives two axis of info to my topside control stamp. Full left on the joystick will result in a 0 while full right gives a 254. The same is true for forward and backward motion. The joystick centers to roughly 127 on both axis. The third thruster is for the dive function and will more than likely be a potentiometer with the center being off (127), a turn of the pot to the left would result in thruster turning one direction and oposite for a turn to the right. I'd like to be able to send this info down my network to the ROV with the second stamp inside. A little preportional control of the speeds would be nice, not simply on and off but a couple of steps in between.

The joystick has a momentary contact button which is currently tied to an input on the topside stamp. I'd like to be able to open and close a small gripper on the ROV with it.
My ROV also has an HM55B compass and I'd like to be able to "pull" data back up from the ROV maybe once a second or so letting me know which way my ROV is pointed. The code will have to be able to put the 75176 into receive mode or transmit mode. A single BS2 pin held high or low does this.

In a nutshell,
I can work out all the motor control and compass coding if I can just get code written to send a few sets of three digit variables down to the ROV and be able to retrieve a single three digit variable back up from the ROV.
'========[topside control]===============
Backward /off /Forward or 0-127-254
Left /off/ Right 0-127-254
Up/off/down 0-127-254
Gripper open/close 0-1
'=========[ROV controller]===============
Act on variables sent down over RS-485 link
send 0-360 back up to topside over RS-485 link.

Any help would be really great.
Thanks.