Shallow Thoughts : tags : usb

Akkana's Musings on Open Source Computing and Technology, Science, and Nature.

Thu, 16 Feb 2012

Arduino Nano -- cute, but sensitive about USB cables

[Arduino Nano] I just got an Arduino Nano. Cute little thing -- I'm looking forward to using it in portable projects. But I had one problem when first plugging it in. It was getting power just fine, and blinking its LED -- but it wasn't showing up as a USB serial port in Linux. dmesg said things like:

usb 1-3.4: new full speed USB device number 7 using ehci_hcd
usb 1-3.4: device descriptor read/64, error -32
usb 1-3.4: device descriptor read/64, error -32
with several different device numbers each time, and an occasional unable to enumerate USB device on port 4 thrown in.

A web search found a few other people seeing this problem on Linux or Linux-based devices, with some people saying that pressing the RESET button multiple times helps. It didn't for me. What solved the problem for me was switching cables. The mini-USB cable I'd been using -- which has worked fine for other purposes, including programming other Arduinos through an FTDI Friend -- apparently was missing something the Nano needs for downloading. With a different cable, dmesg showed a much more civilized

usb 1-3.4: new full speed USB device number 20 using ehci_hcd
ftdi_sio 1-3.4:1.0: FTDI USB Serial Device converter detected
usb 1-3.4: Detected FT232RL
usb 1-3.4: Number of endpoints 2
usb 1-3.4: Endpoint 1 MaxPacketSize 64
usb 1-3.4: Endpoint 2 MaxPacketSize 64
usb 1-3.4: Setting MaxPacketSize 64
usb 1-3.4: FTDI USB Serial Device converter now attached to ttyUSB0

What was wrong with the cable? I did some testing with a multimeter versus a pinout diagram. Didn't get a definitive answer, but I did find that on the cable that doesn't work for the Nano, it was hard to get a solid connection on the D- (#2) pin inside the Type A connector. But since that's the connector that goes to the computer end (in my case, a powered hub), if it wasn't making good contact, I would expect it to show up everywhere, not just with the Nano. Maybe the Nano is more sensitive to a good solid D- connection than other devices.

I'm not really convinced. But Arduino's Troubleshooting Guide suggests: "Try a different USB cable; sometimes they don't work." So I guess they don't know what's special about some cables either.

So if your Arduino Nano doesn't initially connect properly, don't panic. Try a few different cables (everybody has about a zillion mini-USB cables lying around, right? If not, here, have five of mine). The Nano is happily composing random chiptunes as I write this.

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[ 16:24 Feb 16, 2012    More hardware | permalink to this entry | ]

Sun, 22 Jun 2008

Custom ringtones on a Motorola phone, from Linux

I decided to stick a tentative toe into the current millennium and get myself a cellphone.

I sense your shock and amazement -- from people who know me, that I would do such a thing, and from everybody else at the concept that there's anybody in 2008 who didn't already have one.

I really don't think cellphones are evil, honest! (Except in the hands of someone driving a car -- wouldja please just put the phone down and pay attention to the friggin' road?) The truth is that I just don't much like talking on the phone, and generally manage fine with email. The land-line phone works fine for the scant time I spend on the phone, and I have to have the land line anyway (as part of the DSL package) so why pay another monthly bill for a second phone?

Prepaid plans looked like just the ticket, and that's what I got. With a cute little Motorola V195s. New toy! Rock! It can take custom MP3 ringtones and Java games ... but of course I don't want theirs, I want to make my own. So I wanted to talk to the phone from Linux.

The charger plug was a familiar shape -- looked a lot like a standard mini USB connector. Could the hardware be that easy? Sure enough, it's a standard mini USB. Kudos to Motorola for making that so easy! Now what about software?

My initial web searches led me down a false trail paved with programs like wammu and gnokii. I learned that I needed to enable ACM in my kernel (that's the modem protocol most cellphones use over USB), so as long as I was building a new kernel anyway, I grabbed the latest tarball from ( With that done, I was able to talk to the phone with gnokii, but the heavily Nokia-oriented program didn't show me much that looked useful.

Moto4lin is the answer

I set the project aside for a while. But half a week later while looking for something else, I stumbled across moto4lin, which turned out to be exactly what I needed. I had to run as root, or else when I try to connect, it prints on stderr:

sendControl Error:[error sending control message: Operation not permitted]
) but I'm sure that can be solved somehow.

So run as root, click Connect, click File Manager if you're not already in that mode, then click Update List and it reads the files. Once they're there, you can click around in the folder list on the left looking for the audio files (on my phone, they're in a directory called audio somewhere under C, not A). Excellent!

Creating a ringtone leads to a kernel debugging digression

Okay, now I needed a ringtone. I wanted to use a bit of birdsong, so I loaded one of the tracks I use for tweet into Audacity and fiddled semi-randomly until I figured out how to cut and save a short clip. It would only save as WAV, but lame clip.wav clip.mp3 solved that just fine.

(Update: the easiest way is to select the clip you want, then do File->Export Selection...)

Except ... somewhere along the way, the clips stopped playing. I couldn't even play the original ogg track from tweet. It *looked* like it was playing ... it found the track, printed information about it, showed a running time-counter for the appropriate amount of time ... but made no sound.

It eventually turned out that the problem was that shiny new kernel I'd downloaded. A bug introduced in 2.6.24 to the ymfpci sound card driver makes Yamaha sound cards unable to play anything with a bitrate of 44100 (which happens to be the typical CD bitrate). After a lot of debugging I eventually filed bug 10963 with a patch that reverts the old, working code from

Ringtone success

Okay, a typical open source digression. But while I was still trying to track down the kernel bug, I meanwhile found this Razr page that tipped me off that I might need a different bitrate for ringtones anyway. So I converted it with:

lame -b 40 mock.wav mock.mp3
(which also made it playable on the new kernel.) I also found some useful information in the lengthy Ubuntu forums discussion of moto4lin.

In the end, I was able to transfer the file easily to the motorola phone, and to use it as my nifty new ringtone. Success! Too bad nobody ever calls me and this phone is mostly for outgoing calls ...

Now to look for some fun Java apps.

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[ 20:27 Jun 22, 2008    More linux | permalink to this entry | ]

Sat, 31 May 2008

How to fix usbview and /proc/bus/usb in Ubuntu Hardy

Ah, I so love progress. I was working with powertop to try to make my system more efficient, and kept seeing a USB device I didn't recognize showing up as a frequent source of wakeups. lsusb didn't show it either, so I tried firing up usbview.

Except it didn't work: on Hardy it brings up an error window complaining about not being able to open /proc/bus/usb, which, indeed, is not mounted despite being enabled in my kernel.

A little googling showed this was an oft-reported bug in Ubuntu Hardy: for instance, bug 156085 and bug 151585, both with the charming attitude I so love in open source projects, "No, we won't enable this simple fix that reverts the software to the way it worked in the last release; we'd prefer to keep it completely broken indefinitely until someone happens to get around to fixing it right."

Okay, that's being a little harsh: admittedly, most of the programs broken by this are in the "universe" repository and thus not an official part of Ubuntu. Still, why be rude to users who are just trying to find a way around bustage that was deliberately introduced? Doesn't Ubuntu have any sort of process to assign bugs in universe packages to a maintainer who might care about them?

Anyway, the workaround, in case you need usbview or qemu/kvm or anything else that needs /proc/bus/usb, is to edit the file /etc/init.d/ and look for the line that says:

# Magic to make /proc/bus/usb work
Uncomment out the lines immediately following that line, then either reboot or run the last command there by hand.

(In case you're wondering, usbview showed that the USB device causing the powertop wakeups was the multi-flash card reader. I'm suspecting hald-addons-storage is involved -- powertop already flagged hal's cdrom polling as the number-one power waster. I don't know why the flash multicard reader shows up in usbview but not in lsusb.)

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[ 21:45 May 31, 2008    More linux | permalink to this entry | ]

Sun, 13 May 2007

Feisty Fawn: The Adventure Continues, with the Visor Driver

When we left off, I had just found a workaround for my Feisty Fawn installer problems and had gotten the system up and running.

By now, it was late in the day, time for my daily Sitescooper run to grab some news to read on my Treo PDA. The process starts with making a backup (pilot-xfer -s). But pilot-xfer failed because it couldn't find the device, /dev/ttyUSB1. The system was seeing the device connection -- dmesg said

[ 1424.598770] usb 5-2.3: new full speed USB device using ehci_hcd and address 4
[ 1424.690951] usb 5-2.3: configuration #1 chosen from 1 choice
"configuration #1"? What does that mean? I poked around /etc/udev a bit and found this rule in rules.d/60-symlinks.rules:
# Create /dev/pilot symlink for Palm Pilots
KERNEL=="ttyUSB*", ATTRS{product}=="Palm Handheld*|Handspring *|palmOne Handheld", \
Oh, maybe they were calling it /dev/pilot1? But no, there was nothing matching /dev/*pilot*, just as there was nothing matching /dev/ttyUSB*.

But this time googling led me right to the bug, bug 108512. Turns out that for some reason (which no one has investigated yet), feisty doesn't autoload the visor module when you plug in a USB palm device the way other distros always have. The temporary workaround is sudo modprobe visor; the long-term workaround is to add visor to /etc/modules.

On the subject of Feisty's USB support, though, I do have some good news to report.

My biggest motivation for upgrading from edgy was because USB2 had stopped working a few months ago -- bug 54419. I hoped that the newer kernel in Feisty might fix the problem.

So once I had the system up and running, I plugged my trusty hated-by-edgy MP3 player into the USB2 hub, and checked dmesg. It wasn't working -- but the error message was actually useful. Rather than obscure complaints like end_request: I/O error, dev sde, sector 2033440 or device descriptor read/64, error -110 or 3:0:0:0: rejecting I/O to dead device it had a message (which I've since lost) about "insufficient power". Now that's something I might be able to do something about!

So I dug into my bag o' cables and found a PS/2 power adaptor that fit my USB2 hub, plugged it in, plugged the MP3 player into the hub, and voila! it was talking on USB2 again.

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[ 21:10 May 13, 2007    More linux | permalink to this entry | ]