Re: [Paparazzi-devel] Filtering Issues? and/was: anyone else having problem with ftdi FT2232H on oneiric?

[Jake Stewart]

I was going to post some of my results after more testing, but maybe this can 
help...

I ordered the cheapest chineese TTL serial to USB adapter I could find.  I 
think it was $3-5.  It's basically a broken out CP2102 chip.  It seemed to work 
fine, but I noticed that my GPS performance (I was using it to communicate with 
the GPS module) was really poor.  I tried using the 3.3V from my discovery 
board to power the GPS instead and the reception got a lot better.  I know the 
3.3V from the Discovery board isn't that clean either since it seems to inject 
noise back into the audio on my computer.

Anyways, I scoped the power from the CP2102 and it looked better than I 
expected but still pretty dirty.  I ended up soldering a capacitor labeled 
KC222M across the 5V USB line to the ground.  This seemed to clean up a lot of 
the noise, and was the best of what I tried.  It's a light blue capacitor and 
looks like a ceramic type, but could be polyester film or tantalum.  You find 
them a lot in power supplies and there's usually at least one on any decent 
size PCB board.

Maybe this can help someone as it worked pretty well for me.  Does anyone else 
have any tips on specific filtering that works well for filtering GPS power or 
signal lines?  I don't think it will be a problem in the plane running on 
battery power, but it would be something good to know.  It sure took me awhile 
to figure out the problem and I was almost ready to assume the GPS antenna was 
fried or it had ESD damage problems.  I'm hoping someone has some experience 
filtering power at GPS frequencies as I think any noise in that range probably 
causes significant signal quality problems.


-Jake


> ----- Original Message -----
> From: Felix Ruess
> Sent: 02/11/12 01:20 PM
> To: Paparazzi devel list
> Subject: [Paparazzi-devel] anyone else having problem with ftdi FT2232H on 
> oneiric?
> 
> Hi all,
> 
> is anyone else having problems with the FTDI FT2232H on oneiric?
> 
> I often don't get anything on the tty for the FLOSS-JTAG serial connection.
> It works right after a reboot, but after unplugging, replugging twice I
> don't get anything anymore.
> It might be coincidence that it doesn't work after replugging twice, but it
> seems to work if I get a device number lower than 8.
> 
> [186861.361114] usb 1-1.1: new high speed USB device number 8 using ehci_hcd
> [186861.461305] ftdi_sio 1-1.1:1.0: FTDI USB Serial Device converter
> detected
> [186861.461398] usb 1-1.1: Detected FT2232H
> [186861.461406] usb 1-1.1: Number of endpoints 2
> [186861.461413] usb 1-1.1: Endpoint 1 MaxPacketSize 512
> [186861.461419] usb 1-1.1: Endpoint 2 MaxPacketSize 512
> [186861.461426] usb 1-1.1: Setting MaxPacketSize 512
> [186861.461823] usb 1-1.1: FTDI USB Serial Device converter now attached to
> ttyUSB0
> [186861.463264] ftdi_sio 1-1.1:1.1: FTDI USB Serial Device converter
> detected
> [186861.463346] usb 1-1.1: Detected FT2232H
> [186861.463353] usb 1-1.1: Number of endpoints 2
> [186861.463360] usb 1-1.1: Endpoint 1 MaxPacketSize 512
> [186861.463366] usb 1-1.1: Endpoint 2 MaxPacketSize 512
> [186861.463372] usb 1-1.1: Setting MaxPacketSize 512
> [186861.463753] usb 1-1.1: FTDI USB Serial Device converter now attached to
> ttyUSB1
> 
> It is definitely not a paparazzi issue, I can't even get anything with cat
> or minicom...
> It also always works on my netbook (still on natty). And my xbee with
> FT232RL usb<->serial converter runs fine (on natty and oneiric).
> 
> Udev loads the driver, creates the devices (and custom symlinks I added)
> just fine.
> 
> So it probably is issue with the driver... but unloading ftdi_sio doesn't
> help either.
> 
> It seems they fixed some FTDI issues in 3.0.0-15.25:
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/897514
> But it didn't solve my issues...
> Tested kernel versions: 3.0.0-15-generic and 3.0.0-16-generic on 64bit
> 
> Did anyone have the same problem? Any ideas?
> 
> Cheers, Felix