USB success/confusion

Archiver

Hi all,

Has anyone played with the FTDI USBMOD2, or had any experience with USB at
all?

I've had mixed results.

I can get data sent from a PC's RS232 port to a Mac's USB port OK,

However, I can't get it to work the other way around.

Whenever a character is sent from the Mac's USB port, I'm getting 255 on the
8 bit bus. The Mac is sending the data correctly, and the USBMOD2 seems to
be operating correctly. It also turns up, correctly ID'ed, in the Apple
System Profiler.

About the only thing I can think of is that the USBMOD2 needs pull up
resistors on it's data ports when in output mode, which seems like a strange
requirement. I would think the data ports are not open collector outputs,
being bidirectional ports...

Any ideas??

Cheers,

Ben.

--
http://www.lennard.net.nz/
Ben Lennard, NCEE, Dip EE

Web Hosting and Electronics R&D

Hm: +64 4 972 7567
Mb: +64 21 536 627
87 Spencer Street
Crofton Downs
Wellington
New Zealand

"To the optimist, the glass is half full. To the pessimist, the glass is
half empty. To the engineer, the glass is twice as big as it needs to be."

No animals were harmed in the transmission of this email, although the
Dog next door is living on borrowed time, let me tell you! Those of you
with an overwhelming fear of the unknown will be gratified to learn that
there is no hidden message revealed by reading this warning backwards.

Archiver

Hi all,

Thanks to those who replied off list.

I figured out the reason why the USB Module wasn't working when receiving
from the Mac's USB port.

Helps if you simplify things and go back to basics sometimes.

I connected a LED array to the data bus of the USBMOD2, and noticed that the
module was indeed loading the data received on to the data bus, but only
briefly.

The fault was with my program.

A simple modification, and it now works.

Full details can be found on my website at http://www.lennard.net.nz/ click
on electronics, then click on the USB link.

The circuit diagram doesn't show WR and /TXE wired up, I will fix that
later, but the two test programs work.

Next step is to integrate the two programs together, and try transfering
files between to different platforms and buses.

cheers,

Ben, Wellington, New Zealand.

--


> From: Ben Lennard <postmaster@s...>
> Date: Thu, 06 Jun 2002 23:04:07 +1200
> To: <basicstamps@yahoogroups.com>
> Subject: USB success/confusion
>
> Hi all,
>
> Has anyone played with the FTDI USBMOD2, or had any experience with USB at
> all?
>
> I've had mixed results.
>
> I can get data sent from a PC's RS232 port to a Mac's USB port OK,
>
> However, I can't get it to work the other way around.
>
> Whenever a character is sent from the Mac's USB port, I'm getting 255 on the 8
> bit bus. The Mac is sending the data correctly, and the USBMOD2 seems to be
> operating correctly. It also turns up, correctly ID'ed, in the Apple System
> Profiler.
>
> About the only thing I can think of is that the USBMOD2 needs pull up
> resistors on it's data ports when in output mode, which seems like a strange
> requirement. I would think the data ports are not open collector outputs,
> being bidirectional ports...
>
> Any ideas??
>
> Cheers,
>
> Ben.
>
> --
> http://www.lennard.net.nz/
> Ben Lennard, NCEE, Dip EE
>
> Web Hosting and Electronics R&D
>
> Hm: +64 4 972 7567
> Mb: +64 21 536 627
> 87 Spencer Street
> Crofton Downs
> Wellington
> New Zealand
>
> "To the optimist, the glass is half full. To the pessimist, the glass is
> half empty. To the engineer, the glass is twice as big as it needs to be."
>
> No animals were harmed in the transmission of this email, although the
> Dog next door is living on borrowed time, let me tell you! Those of you
> with an overwhelming fear of the unknown will be gratified to learn that
> there is no hidden message revealed by reading this warning backwards.
>
>
>