RE: USB DLP2232M CNC, Was Re: Interface. Gauging interest.

Hi Mike,

Sorry I couldn't remember the source!

That certainly sounds simple enough. Then can the USB keep stuffing the
input of the FIFO fast enough so that the 6.5 uS output of the FIFO is NEVER
interrupted? What USB transfer mode do you use? I've read about the
ISOCHRONOS mode that sounds like a likely candidate. HID or COM type?

Do you already have a full CNC controller program written for Windoz, or are
you testing move routines? What language?

How hard is it to "talk" to the USB via your high level language? I've seen
apps that relied on a "virtual comm. port" created by a USB driver. Do you
use that (FTDI driver), or is there a way to talk "USB" to the USB device
directly? (Boy, there is a LOT I've got to try to ketch up on!)

I didn't see a " DLP-2232PB has the FTDI chip, plus a PIC 16F277A " on the
FTDI website:

http://www.ftdichip.com/

It sounds more like the USB PIC, and could be more useful.

Your project hardware also seems to fit into the "USB-CNC-PARALLEL" board
description. Do you have to do much to program the 2232?

Certainly sounds interesting. I'm anxious to see your progress.

Alan KM6VV

>
> Alan Marconett wrote:
> > WHO was doing something with the DLP2232M module? (please contact me)
> I'd
> > like to hear a little more about that. There IS buffering (FIFO). Is
> there
> > an interrupt to clock the data out of the FIFO? Another clock to de-
> couple
> > the output as smooth steps?
>
> That would be me!
>
> Yes, there's buffering, and it seems to work pretty well. I seem to be
> getting a reliable rate of one byte sent out every 6.5us, and my PC is
> not even breathing hard doing the calculations for the step pulses.
>
> Note: no separate clock is needed to output smooth steps -- what's so
> nice about this FIFO mode is that the chip clocks data out every 6.5us
> for you. If you don't send it anything, the last value you sent just
> sits there. The clock rate I'm using right now is 9600 * 16 (153.6kHz).
>
> That makes for a maximum step rate of 76.8kHz, because you have to send
> a zero, then a one, for every step. But, since data is clocked out
> every 6.5us, that means that you can place the slower STEP signals with
> an accuracy of 6.5us (the full resolutions you'd expect with a 153.6kHz
> clock).
>
> If I remember right, that's almost as fast as the Allegro chip in the
> HobbyCNC board can take it.
>
> There is a line available to clock data out of the thing, but I don't
> use it -- the FTDI chip just holds on to the last value, until the next
> one is ready to be clocked out. If you wanted to clock the data stream
> into an external latch, or use that line to interrupt a PIC, you
> certainly could.
>
> In fact, DLPDesign makes such a FTDI+PIC thing, that works exactly like
> that. DLP-2232PB has the FTDI chip, plus a PIC 16F277A. Because of the
> PIC, it costs a bit more ($50 vs $35).
>
> If I get stuck with the 2232 alone, and the pulse train has problems
> coming raw from the 2232 chip, I'll move up to this more expensive
> version, and program the PIC to do the pulses for me.
>
> Info is here:
> http://www.dlpdesign.com/usb/2232m.shtml
>
> Right now, I run the FTDI chip's output lines directly to a female DB-25
> connector, that plugs into a HobbyCNC board, just like a parallel port
> cable would. Something like this:
>
> 2232's
> PortA
> 0 XStep
> 1 XDir
> 2 YStep
> 3 YDir
> 4 ZStep
> 5 ZDir
> 6 AStep
> 7 ADir
>
> The FTDI chip also can do simultaneous reads at that same rate (so, as
> you're writing bytes, the chip is also reading bytes in at the same time
> and sending them back to you), but I'm not doing that sort of thing yet.
>
> Mike
>