FT245BM problem: missing/corrupt data

Hello,

We are facing a corrupt/missing data problem with FT245BM:

If the "pull down on USB suspend" option is enabled in EEPROM, on
startup, we get 126 bytes of garbage followed by the first byte from
host. Subsequent bytes come across fine.

If the "pull down on USB suspend" option is NOT enabled in EEPROM, the
first byte from host is never received. Subsequent bytes come across
fine.

The algorithm we are using to read is the following:

1. Wait for RXF to go low
2. Set RD low
3. Wait for 200ns
4. Read data
5. Set RD high


- FT245BM connected to ATmega16
- Configured as bus powered device (100mA)
- VCC for the ATmega64 is switched using MICREL 2025-2BM power switch.
Same as Fig 11 (Page 21) on the datasheet but with power switch IC
instead of MOSFET.
 
Any workarounds, debugging tips?

Thanks,
Abdul

<abduln@gmail.com> wrote in message
news:1129930754.828215.11840@g44g2000cwa.googlegroups.com...
> Hello,
>
> We are facing a corrupt/missing data problem with FT245BM:
>
> If the "pull down on USB suspend" option is enabled in EEPROM, on
> startup, we get 126 bytes of garbage followed by the first byte from
> host. Subsequent bytes come across fine.
>
> If the "pull down on USB suspend" option is NOT enabled in EEPROM, the
> first byte from host is never received. Subsequent bytes come across
> fine.

Have you asked the technical support of FTDI? Their support is very good.

Meindert

Yes, we did. But they are gone for the weekend. And we have a tight
deadline :<

How long is your USB cable?
Do you have capacitors at the USB connector?
Is your FT245 TST pin connected to GND?

Best regards
Tsvetan
---
PCB prototypes for $26 at http://run.to/pcb (http://www.olimex.com/pcb)
PCB any volume assembly (http://www.olimex.com/pcb/protoa.html)
Development boards for ARM, AVR, PIC, MAXQ2000 and MSP430
(http://www.olimex.com/dev)

I've had problems with resetting or turning off my project with 
HyperTerminal running to the USB module. HyperTerminal locks up, no comms, 
and refuses to shut down. My laptop is unable to shut it down from the 
control panel, and the laptop itself is unable to fully shut down - I have 
to pull the power plug and the battery.

I reckon their FT245BM chip and software needs more work to become robust... 

"Meindert Sprang" <mhsprang@NOcustomSPAMware.nl> wrote:

>Have you asked the technical support of FTDI? Their support is very good.

Really? When evaluating USB/232 chips, I just showed them, how I can
lock up their FT232-VCP-driver. Easily. Each time I try. Gave them
some Portmon-logfiles. Offered to give them a sample program.

Guess, what happens? They told me to try their newest (beta-)driver.

Same procedure again. Guess, what happens? They thanked for the
problem report.

This was about 1,5 years ago. Their driver, which isn't beta anymore,
still locks up.

If you call this "very good support", it's one, I can easily live
without.

I ended with a silabs chip. No hazzles, responsive and honest support.

Andreas
-- 
A clever person solves a problem.
A wise person avoids it.
- Einstein 

"Kryten" <kryten_droid_obfusticator@ntlworld.com> wrote:

>I've had problems with resetting or turning off my project with 
>HyperTerminal running to the USB module. HyperTerminal locks up, no comms, 
>and refuses to shut down. My laptop is unable to shut it down from the 
>control panel, and the laptop itself is unable to fully shut down - I have 
>to pull the power plug and the battery.
>
>I reckon their FT245BM chip and software needs more work to become robust... 

With a FT232, I experienced lock-ups also. I was able to continue
working by
1) disconnect the USB device.
2) wait some seconds, about half a minute, IIRC.
3) shut down the locked application with the task manager.

Still annoying, but no show stopper.

If I tried to shut down the application before disconnecting and
waiting, I ended with the same problem as you. Unrecoverable lock-up.

Andreas
-- 
There's no time to stop for gas, we're already late.
- Karin Donker

We were having tons of disconnects and driver lockups with the FT245BM and
FT232BM chips when connected to USB 2.0.

We adding 47pF caps to ground on USBDP/USBDM, and a 470nF cap connecting USB
shield to ground.  Testing in our office this eliminated 100% of our
problems.  In the field it eliminated 90% of the problems, as our products
are used in an environment prone to static.  We then went up to 100pF caps
on USBDP/USBDM, this eliminated 99% of our problems.

The FTDI documentation, at the time we were doing our design, didn't clearly
mention the need for these caps.  Only the most recent commercial products
using the FT232/245 have any of these caps, and most still don't have the
470nF cap connecting USB shield to ground.

When we initially contacted FTDI support they acted like we probably had a
flaw in our hardware design.  I pointed out that we were using the DLP245PB
module which would fail even without the rest of our design attached.  I was
also able to reproduce the error on a US232B/LC the evaluation USB-to-Serial
converter that they sell.  Then they recommended that we add the caps
mentioned above.  Neither the US232B/LC or the DLP245PB module, have the
caps.

Regards,
Ron Belknap

Ron_Belknap@hotmail.com

"Andreas Hadler" <Andreas.Hadler@t-online.de> wrote in message
news:40gkl193esd81s60j0va58c7cc1ps48sfl@4ax.com...
> "Meindert Sprang" <mhsprang@NOcustomSPAMware.nl> wrote:
>
> >Have you asked the technical support of FTDI? Their support is very good.
>
> Really? When evaluating USB/232 chips, I just showed them, how I can
> lock up their FT232-VCP-driver. Easily. Each time I try. Gave them
> some Portmon-logfiles. Offered to give them a sample program.
>
> Guess, what happens? They told me to try their newest (beta-)driver.
>
> Same procedure again. Guess, what happens? They thanked for the
> problem report.
>
> This was about 1,5 years ago. Their driver, which isn't beta anymore,
> still locks up.
>
> If you call this "very good support", it's one, I can easily live
> without.

Well, I never really had problems with the chips and drivers. Only once when
a laptop locked up when going into sleep while a virtual serial port was
opened. A new driver solved it. But I had a few questions about odd
baudrates aswered very quickly. Also they helped me well when I wanted a
special version of the OS X driver with special baudrate behaviour on
certain PID and all that. No problem, all could be done and was done in no
time.
So in that, my experience with FDTI is good.

> I ended with a silabs chip. No hazzles, responsive and honest support.

Mmmm.... I thought about changing to that one too.

Meindert

Cable is about 3 feet long.
No capacitors on the USB connector
TST pin is connected to ground