Hi, I am new to the Roomba community. Also pretty new to electronics but just finished my project of controlling my HVAC system from my openwrt Asus-wl500gp router running OpenWRT (I have quite a bit of software experience).

In any case, my plan is to control a Roomba, not a Create as I would like it to vacuum, from my router. Although I am aware of the availability of RooTooth and USB bluetooth adaptors for the router, I would prefer Zigbee mostly because it would be more fun to make and also the range on the Xbee 2.5 modules is slightly better than bluetooth (133 vs 100 ft - the former is perfect for me the latter a bit too short).

I found fairly step-by-step instructions for hooking up an Xbee module to a prototype board that hopefully I will be able to follow without too much difficulty. I was thinking of altering the schematics to have a Roomba-compatible mini-DIN connector on the prototype board, but was not able to find something like this breakout board for a 7-pin Mini-DIN connector. Is there one available or how can I hook up a 7-pin mini-DIN connector to the same prototype board in the Xbee module prototype board instructions, as this would make the entire Roomba side of the circuit fit on one prototype board (based on the manual for the Xbee module it seems I can just have "transparent operation" where no configuration will be needed from the Roomba side, thus no controller; is this incorrect?)

On the router side, I am thinking of soldering a 4 pin connector of some sort to the motherboard which has a 3.3V UART on it already and then making a simple prototype board that will hook up to this connector and keeping it outside the router (I am thinking this will improve the range and I'm not sure if the antenna on the Xbee 2.5 module I am interested in will fit inside the case of the 500gp). 

In any case I was wondering what you thinking about these plans, as they are currently in the nascent stage. Am I naive in thinking I can hook up an Xbee to the Roomba without any sort of controller on the Roomba side as described above? Any suggestions on a 7-pin DIN breakout board and connector? Any other general comments?

Thank you so much

Misha

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the range on the Xbee 2.5 modules is slightly better than bluetooth (133 vs 100 ft - the former is perfect for me the latter a bit too short).

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As I understood the RooTooth is a class 1 device with a range of 100 meters (NOT ft) which would be much better than the Xbee.

Regards,

Dirk 

"In any case, my plan is to control a Roomba, not a Create..."

Perhaps this issue is best posted on a Roomba board?

Thanks for the comment. I was advised to post here on a roomba board as I was told there are some people in these forums that have successfully used Xbee boards and my understanding is that this would be a similar proposition (the same?) for both Roomba and Create. Also thank you for the RooTooh comments I wil check on this.

Misha

I think your idea should work just fine.  XBee's in Transparent Mode will work perfectly, I do it all the time to control my Create remotely with XBee's (my preferred radio) on both sides.  Just put a 3.3v regulator with the miniDIN and a 1k resistor on the XBee's DataIN to limit the 5v signal from the roomba's serial port.

Hi Joe, thanks a lot for your response. Two questions for you:

(1) Do you hook up device detect to anything or do you leave it unconnected? If I wanted to hook it up, do you think one of the digital I/O pins would work (although I guess I would have to get another regulator for that pin) or is that not a good idea?

(2) Can the Xbee module be configured completely in a remote fashion (without _ever_ sending any commands from the Roomba, not even initially) or is this impossible and should I adapt a solution that allows the Xbee module to be hooked up to something else (no soldering it directly) so that I can reconfigure it if need be? (This seems like a better idea anyway as it is $25 each).

Thanks

Misha

I'm not sure what "device detect" you are talking about.  All you need to talk to the Create from an XBee is Power, Ground, RX, and TX.  You could connect an XBee's Digital Output to the Power Toggle so you could turn the Create on/off remotely.  You could even connect the Dock Sense output from the Create to an XBee Digital Input (use a resistor when going from Create output to an XBee input, including the Create TX to XBee DIN).  No need to regulate the power in, just put a resistor to limit the current.  (use a 3.3v regulator for the XBee's main power though)

You can not configure an XBee remotely, you must issue the AT commands from it's local serial port.  Odds are, once you've configured the XBee, then move it over to the Create, you'll probably not need to reconfigure anything anyway.

Hi Joe,

Thanks for the info again. Very helpful. I checked on the Create Open Interface manual and I guess this is where the Create and Roomba differ as far as "Device Detect." It is the same as the Baud Rate Change pin on the create, and is titled "Device Detect input (active low) - used to wake up Roomba from sleep" (it also works for baud rate change). However, apparently unlike the Create, where only RXD and TXD use 0-5V logic, on the Roomba "RXD, TXD, and Device Detect pins use 0-5V logic." In a Python code sample, they illustrate a situation in which, e.g., the Device Detect is connected to the PC'S RTS line via a level shifter and they toggle the RTS line to program it for baud (it does baud changes too).

So with this info would I need a separate regulator for it since it operates on 0-5V logic. Obviously it's output only, but I wonder if a 3.3V output is enough to make it work, especially if it is active low it may be always active on 3.3V not sure. Anyhow, sorry if this is a really dumb question, but I'm just new to this and want to be sure before I fry anything. I can also try asking on Roomba forums about this Device Detect if you think it will be helpful.

Thanks a lot for all your help.

Misha

You only need to regulate the Create Power down to 3.3v for the XBee's main power.  The 3v output from an XBee Digital Output can be directly connected to a 5v input on the Create.  It will work and it won't hurt anything.  The XBee is putting out TTL compatible levels, which is what the Create is expecting.  When you are connecting directly to a PC Serial Port then Yes, a level shifter is needed to convert the RTS line from RS-232 leves to TTL levels.

5v and 3.3v devices are usually compatible when you are talking about logic-levels.  The on/off threashold for TTL is typically 1.5v (2.5v for CMOS devices).  Either way, 3v devices handle 5v I/O just fine.

Just remember to put a 1k resistor in series for any 5v outputs to 3v inputs to prevent heating things up on the 3v device.

Thanks Joe, as always that is very helpful. I think that pretty much makes me clear on planning the Roomba side of things (still doing a bit of thinking abot the exact connection to the router's UART but pretty much is straight through, need to figure out if I need to cross TX and RX or not and whether I'd like to have the possibility in the future of using both serial ports the router UART provides rather than just hooking up one directly to Xbee and having to go back in later on when I need another serial port for something).

Misha