FT232RQ and a Parallax Stamp

Bill Chennault

All--

Currently, my BIG DEAL is an RS-485 interface from my BS2px24 (max. 19.2kbs) to the AX-12 servo, which has a powerup default of 1mbs. I suppose one might change the default powerup·baud rate from 1mbs to 19.2kbs on all the AX-12s connected to the Stamp via RS-485, but it seems much more elegant to make the Stamp communicate to the AX-12(s) at 1mbs.

Here is a neat part that MIGHT talk to Parallax's USB2SER and thence to the AX-12 network of servos: the FTDI MM232R module which uses the FTDI FT232RQ.

However, I am not smart enough either to do it, or to speculate intelligently on whether it can be done. Comments are more than welcome and a circuit showing me how to plug this baby into my BOE breadboard area would be IDEAL! [noparse]:)[/noparse]

Merry Christmas!

--Bill

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bennettdan

The Stamp manual says a says the BS2px will communicate at 115.2k..maybe someone has a project that they have used such a baud rate...

Sarten-X

I've used it for communication between two stamps, but nothing else...

allanlane5

All the BS2 flavors are kind of 'speed limited'. Plus, the baud rates built on-board are what they are -- while it might be more 'elegant' to up them, it's also WAY more difficult than you might imagine. For instance, you'd need a custom firmware modification on the BS2 -- and I don't think Parallax DOES custom firmware modifications for individual customers.

Personally, I think you're lucky you can change the baud rates on your servo controller to something the BS2 will support.

Also, it looks like you can command this "servo" (RS-232 controlled device, clever) to have a delay between when it gets its completed message and when it answers.· You may need to tweak this value too, to give your BS2 time to get into its "SERIN" keyword to read the response.· A stock BS2 would take about 300 uSec to begin execution of the SERIN command.· That's the slowest, of course.

Post Edited (allanlane5) : 12/11/2006 3:00:58 PM GMT

Bill Chennault

allanlane5--

Last night, as I lay my head down to sleep, I thought, That was sure a dumb idea!

Since the AX-12 may be set to default at about any baud rate between 9.6kbps and 1mbps upon power-up, I will just use a PC to set it (or the CM-5 controller). I have been promised a "USB2RS485" for the AX-12 "real soon, now."

Hopefully, the next time I post something about the AX-12, it will contain facts.

Thanks for thinking of this. I wondered last night where in the world a crystal might be on the Stamp that would allow for up to a 1mbps baud rate. Although I know little of these things, it seems like one would have to be available on the Stamp to make a dumb idea like this work.

Speaking of dumb ideas, doesn't it sound like a dumb idea to build a great (on paper, anyway) servo like the AX-12 and then set is default, power-up baud rate at 1mbps?

--Bill

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You are what you write.