Jaychadw
United Kingdom
Asked
— Edited
I was wondering if anyone had a simple solution for adding more digital connections to the controller. One idea I had was to link an arduino to it via i2c, although I don't know where to start to do that.
I need to increase the connections by about 6 ( making 26 ) minimum.
For the price of another EZ-B (OK I know they are currently not available but hang in there), which is only going to be about £30 more than any expander, you get native support for all 20 digital ports, 8 more analogue ports and no headaches.
I looked in to using an I2C expander, the datasheet wasn't worth the paper it was printed on, I'm yet to get this to work for the simplest of tasks let alone using it for sensors etc.
Arduino add on could work but do you really want to be writing the code for the Arduino that allows ARC to control it via the I2C port?
It's been discussed before, it'll be discussed again I'm sure, but after a lot of research and messing around (not to mention throwing down £30 on an I2C expander that doesn't work very well) personally speaking I'll always advise a second EZ-B over any other method.
It would of just been a nice cheaper option. Plus a basic script can be written on them to listen for servo positions via its serial port.
I did think about simply making a little circuit that could switch operations of servos using a servo if you get me.
if the control servo was at position A, d0-5 operates servo's 1 - 6.
if the control servo was at position B, d0-5 operates servo's 7 - 12 and so on.
Other positions would then offer a variety of servo combinations.
Just had trouble thinking of the best way to do it.
Scripting i'm happy with. even if its a bit of a ball ache.
SD84
It may be possible to connect the USB to the EZ-B through some type of simple serial connection method however the EZ-B serial is only monodirectional, you can send but it cannot receive which may cause problems.
Also, the SD84 is £53.82 plus VAT and shipping which is more expensive than the $69 plus shipping of an EZ-B.
The SD21 on Robot Electronic's site is I2C controlled and since Tony has recommended it in another post it's safe to say that control is simple. It may pay to look in to using one of those. Or for a cheaper option the SD20 which Tony has mentioned and build yourself a nice little circuit to expand the ports via I2C.
The native controls issue would still apply but with I2C, provided the info is clear, it's simple, quick and easy to script.
Anything that costs more than an ez-b is next to pointless for me as im looking for the cheapest possible option.
I will post back when I've looked
The 6 port micro maestro is $19.95. The 12 port mini maestro is $29.95.
Check out the forum discussion I started (http://www.ez-robot.com/Community/Forum/posts.aspx?threadId=4259). I have been working on other parts of my robot so I have not gotten back to the pololu yet. I want to try using a virtual servo and monitoring script to try and allow the ARC user interface more visual control of the pololu maestro controlled servos. My other approach is a Slide script which might work quite well.
Pololu also has a serial servo controllers that might do the job. Eight servo ports by using one EZ-B port for serial output to the controller. http://www.pololu.com/catalog/product/0207/resources still $19.95. The maestro can control digital outputs as well as servos which is more what I wanted. I don't have any experience with the serial servo controller, but it looks like it might be what you need.
As noted using two EZ-Bs is the easiest way as it gives you direct access to all of the ports in the user interface. ARC scripting for the pololu hardware is not difficult and you do not need to use the pololu maestro scripting features if all you need is more ports. The issue is the pololu connection is one way(EZ-B to Pololu). The ARC scripts tell the pololu what to do. The pololu has no feedback path to provide status information on its ports. With two EZ-Bs you get the feedback visually on the computer screen.
Seems a nice little chip.
@RobertL184 I have looked at these before. But I thought that they were only compatible via USB. I didn't realise they could be operated digitally.
I am personally scripting my robot in c#. One way communication is fine for what I need.
I will re look into the maestro now. I
I was talking about using the sd84 with the EZB not replacing the EZB. But, it looks like they have more simple ones. The sd84 worked off of the USB port.
Same damn site I was looking on *confused*