Author Topic: ft232r problems.  (Read 3767 times)

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Offline dunkTopic starter

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ft232r problems.
« on: June 03, 2007, 07:11:52 PM »
hey guys,
has any one got any experience with the ft232r USB to UART chip?
http://www.ftdichip.com/Products/FT232R.htm
from the datasheet it looks fairly straight forward.
reading about it on the internet i haven't found anyone else with the similar problems to me. indeed, it seems from all reports a fairly straight forward component.

so, here's the background,
i have made and etched the attached circuit:

i am reasonably sure there are no bad connections or shorts.
when i plug it in on a linux computer it does not appear under /proc/bus/usb/devices.
when it is first plugged in (or when the uhci_hcd driver is removed and reloaded) i get the following output to the sys log at the same time as the RX and TX LEDs flash:
Code: [Select]
[17180187.476000] usb 3-2: new full speed USB device using uhci_hcd and address 2
[17180187.596000] usb 3-2: device descriptor read/64, error -71
[17180187.820000] usb 3-2: device descriptor read/64, error -71
[17180188.036000] usb 3-2: new full speed USB device using uhci_hcd and address 3
[17180188.156000] usb 3-2: device descriptor read/64, error -71
[17180188.380000] usb 3-2: device descriptor read/64, error -71
[17180188.596000] usb 3-2: new full speed USB device using uhci_hcd and address 4
[17180189.004000] usb 3-2: device not accepting address 4, error -71

so, my hypothysis is that the ft232r must be functional to some extent as the LEDs flash when the relevant driver is reloaded.
i suspect that there some sort of interference going on that is preventing communication between the ft232r and the host computer.

i will try a different USB cable if i can pick one up at work and if that doesn't work, etch another board and rebuild but i'm reasonably confident the circuit is good.

questions:
has anyone used this chip before and was it as temperamental as i'm finding it?
could someone compair my schematic to the datasheet and see if i'm missing anything obvious please? (it wouldn't be the first time a dumb typo on my part has had me scratching my head for days...)

cheers,

dunk.
« Last Edit: June 03, 2007, 07:14:22 PM by dunk »

Offline JonHylands

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Re: ft232r problems.
« Reply #1 on: June 04, 2007, 06:07:44 AM »
Dunk,

I use that chip on my BrainBot robot, interfacing to a gumstix verdex. The driver was included, but disabled, so we had to enable it (which on the gumstix required a re-build).

Once I had that done, when I plugged it in I get a bit of text on the console (don't remember off the top of my head what), which was more than what I got when the driver wasn't enabled.

Okay, I just booted up my gumstix, and this is what I get when I plug in the FT232 (once it has fully booted up):

# usb 1-2: new full speed USB device using pxa27x-ohci and address 6
usb 1-2: configuration #1 chosen from 1 choice
usbcore: registered new driver usbserial
drivers/usb/serial/usb-serial.c: USB Serial Driver core
drivers/usb/serial/usb-serial.c: USB Serial support registered for FTDI USB Serial Device
ftdi_sio 1-2:1.0: FTDI USB Serial Device converter detected
drivers/usb/serial/ftdi_sio.c: Detected FT232BM
usb 1-2: FTDI USB Serial Device converter now attached to ttyUSB0
usbcore: registered new driver ftdi_sio
drivers/usb/serial/ftdi_sio.c: v1.4.3:USB FTDI Serial Converters Driver

- Jon

Offline dunkTopic starter

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Re: ft232r problems.
« Reply #2 on: June 04, 2007, 07:11:11 AM »
hi Jon,
yea, it's not a driver issue as i should be able to see the vendor id and the device id under the /proc/bus/usb/devices file for any USB device even with no driver loaded.
as a result i'm reasonably sure it's a hardware problem.

dunk.

Offline JonHylands

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Re: ft232r problems.
« Reply #3 on: June 04, 2007, 07:59:23 AM »
One issue I had when I was building my first FT232 board was in the datasheet there are two different layouts for the chips, with completely different pin numbers depending on whether you're looking at the MLF package or the TSSOP package...

- Jon

Offline dunkTopic starter

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Re: ft232r problems.
« Reply #4 on: June 04, 2007, 12:23:34 PM »
yea, i'm using ft232rl which uses the SSOP package format, but i am wondering if i'm doing something dumb like that.

dunk.

Offline JonHylands

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Re: ft232r problems.
« Reply #5 on: June 04, 2007, 12:42:14 PM »
One thing to try is plug it into a Windows XP machine - the drivers for that chipset are either included, or easy to find, and it works nicely.

That will at least sort out if it is a driver issue versus a hardware issue...

- Jon

Offline Admin

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Re: ft232r problems.
« Reply #6 on: June 04, 2007, 02:06:53 PM »
So looking at the offered connection diagrams (such as on pg 23 of the datasheet), but they dont use the reset pin . . . as a matter of fact they never do in examples . . . and Im just curious why you do this wierd voltage divider from the USB power to send 3.57V to the reset pin . . . why not just tie it to VCCIO like the datasheet says?

ignore this comment if Im being dumb, Ive never used this chip before . . . ;D


And unrelated to your problem, but Im just curious why you decided not to use the 5V from USB to power the board?

Offline JonHylands

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Re: ft232r problems.
« Reply #7 on: June 04, 2007, 02:12:20 PM »
Yeah, my setup is a lot simpler than dunks - I power the entire setup off the USB bus.

- Jon

Offline dunkTopic starter

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Re: ft232r problems.
« Reply #8 on: June 04, 2007, 03:35:50 PM »
Quote
So looking at the offered connection diagrams (such as on pg 23 of the datasheet), but they dont use the reset pin . . . as a matter of fact they never do in examples . . . and Im just curious why you do this wierd voltage divider from the USB power to send 3.57V to the reset pin . . . why not just tie it to VCCIO like the datasheet says?
so i went with device power rather than USB power for no particular reason. just seemed like the right call at the time as there is allready a perfectly good 5V source elsewhere in the circuit. (it's illustrated on p20 of the datasheet.)
the idea being that the FT232 doesn't come out of reset until it's plugged into the USB port so everything initialises properly. (or not in my module's case...)

i have noted though that Jon had better luck than me using this chip in bus powered mode. i'll try building a version that way round.

Quote
And unrelated to your problem, but Im just curious why you decided not to use the 5V from USB to power the board?
so i'm going to have several AVRs, servos, motor controllers, sensors, bells and whistles on this project.
(it's my latest robot's interface boards finally being built. drum roll please...)
the combined load would be far too much current for the USB port on my embedded controller.

Quote
One thing to try is plug it into a Windows XP machine - the drivers for that chipset are either included, or easy to find, and it works nicely.
so i'm planning on bringing the module along to work tomorrow to see if i can borrow a windows machine somewhere.
we usually pick on windows users at work but they do have their uses....

dunk.

Offline dunkTopic starter

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Re: ft232r problems.
« Reply #9 on: June 04, 2007, 05:24:19 PM »
ok, i feel dumb.
so while rewiring the board to take power form the USB port (which made no difference) i decided to give all the contacts on the FT232 chip a good roasting with my soldering iron.
after that the whole thing works fine.
so, obviously either a bad connection or a solder bridge underneath the chip. (but not one bad enough for me to find with a multimeter.)
either way, it works now.

so, happy days. dunk's next robot is one step closer...

dunk.
(new to surface mount components.)
((thanks Jon and Admin for the suggestions and moral support.))
« Last Edit: June 04, 2007, 05:26:34 PM by dunk »

 


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