Homebuilt ROVs Forum

Deakel wrote: ordered 4 new rs485 surface mount chips for converting Arduino signal to rs485 and back to rs232. The 2 arduinos are communicating through 100' of cat 5 cable full duplex.

Hey Deakel,
Why 4 chips? Backups?

With your current coms that is working with 100' of cat5, is that rs232 or rs485?

Thanks,
Ryan
"KR2_Diving"

Hey Ryan,

I'm like the eager new kid jumping up and down trying to demonstrate new found knowledge....lol, but until we get a real answer, I'm going to guess and say the 4 chips were to achieve full duplex.

The MX485 chips, used for converting RS232 to RS485 only operate at half duplex (cannot tx and rx at the same time). There are many work arounds for this with code, but if the 'Meager Machine' has achieved full duplex, and is using 4 chips, I'm guessing they have doubled up to create two half-duplex lines (which would give them full-duplex).....Can't wait to find out more! Oh, and sorry to jump in like that... Of course, if he's using the MX488 chip (I think I got that right), they are full duplex already and I'm certainly wrong.

Sounds reasonable enough to me. I don't know anything about RS-485, though, so I don't think my opinion counts for much! I just use RS-232 most of the time.

I'm confused though, Deakel said they were for converting the RS-485 to RS-232 for the Arduinos, but Arduinos need a TTL signal...?

max485 converts ttl to 2-wire(half duplex) RS485 signals. this need a extra signal/function to flip the communication each way. (RTS / TX enable)
Max488 converts ttl to 4-wire(full duplex) RS485/RS422 signals. no extra need for special code or anything. can be used for extending almost any ttl signal.
the arduino pin 0 and 1 is rs232 ttl signals.

Sorry guys I been real busy lately. The Arduino's use TTL for communication which is rs232, but you can only get like 15' distance on communication. (I dont wanna rely on a laptop out on the water so Im just using Arduino's for all the work). If that makes sense. So the rs485 chips convert that signal for longer distance communication up to 1000' I think and yes i use 4 chips for full duplex communication two on each end for send/receive. I found this site that helped with the setup. http://pskillenrules.blogspot.com/2009/ ... rs485.html
It works but the code is getting tricky and you basically use the write and print functions built into the Arduino code. And send a character to be received on the other end to run the appropriate function. I dont like narrating videos but heres a short video. I can post what code I have so far if it would help.
http://www.youtube.com/watch?v=fPbQnK5e ... e=youtu.be

Hey Deakel,

I just wanted to say thanks for taking the time to go into a little more detail on your communications setup. I had already ordered MAX485 but, after watching your you-tube, and with a little encouragement from KR2 (Ryan), I've ordered some MAX488 so I can play around with full-duplex (without using 4 chips). Of course, I'll experiment with both and see how they differ. You also inspired me to order a compass sensor which I'm eager to setup like you have.

Great to actually see the project in action! Thanks again.

Anyway I can help. Keep in mind with the compass don't solder anywhere near it or you'll destroy it. I did that to the first one had to order another one. I used a surface mount IC and cut it to build a square then made a circuit on a breakout board from radio shack then plug the compass into that. And the compass works so that the direction its reading is OFF or low so you need some pull up resistors so the arduino can tell which input is off.

I found a good 12v brushed esc for $40, water resistant as well.
http://www.proboatmodels.com/Products/D ... ID=PRB2314