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1  Hardware and U-Boot firmware / Hardware / Re: Using the second port as ... usb? on: July 30, 2009, 10:23:07 AM
The problem is the second port is a USB device, and you want a port that's a USB host.  To simplify slightly, the port goes the "wrong way" and needs to be connected to another computer, not to a USB device like a keyboard or flash drive.  If you need more USB ports, just connect a hub to the main (host) port.
2  Linux Stuff / General Linux questions / Re: usb audio dongle only plays right channel on: July 24, 2009, 10:13:42 PM
I fixed my audio problem with alsamixer (from apt-get install alsa-utils).   Running it apparently fixed whatever was set wrong with the sound settings.  I'm guessing alsa had one channel muted for some reason.
3  Linux Stuff / General Linux questions / usb audio dongle only plays right channel on: July 24, 2009, 11:51:00 AM
I tried a USB audio dongle (Turtle Beach Audio Advantage Micro) and mpd with my plug, but for some reason, only the right audio channel plays.  It works fine on Windows with both headphones and speakers, so it's not a hardware issue.  I've read over the PlugWiki USB Audio page (http://www.openplug.org/plugwiki/index.php/USB_Audio) and searched on Google a bunch, but I can't figure out why only one channel would play.  Any suggestions?

(One problem I did figure out was the audio quality.  For some reason, the default mpd config file plays one-channel audio but with terrible crackling sounds.  Uncommenting the alsa audio_output lines in /etc/mpd.conf as described in USB_Audio got rid of the crackling and reduced CPU load.)
4  Linux Stuff / Kernel / Re: Request for upcoming 2.6.30 on: July 02, 2009, 02:44:18 PM
I'd like to have the ibmcam webcam driver.  Does your 2.6.30 kernel support loadable modules or would this need to be compiled in?

Thanks, Ken
5  General Category / Success stories / Arduino and SheevaPlug for hardware hacking on: July 01, 2009, 11:44:37 PM
I started using an Arduino microcontroller board and a SheevaPlug together, and I'm very happy with the combo.  The Arduino provides low-level analog and digital I/O, and the SheevaPlug provides computation, storage, and web service.  All I needed to do was install a kernel with usb serial support, and then connect the two with a USB cable.

More details are on my blog at http://arcfn.com/2009/06/arduino-sheevaplug-cool-hardware.html
6  Hardware and U-Boot firmware / Hardware / Re: SATA controller on: July 01, 2009, 02:48:39 PM
I don't know if the SATA data pins are accessible, but it looks like the SATA LED indicators could be available.  Of course, without the data pins, the SATA LED indicators aren't any use.   But maybe someone else can figure out the data pins.

Based on the hardware specification [1] and the schematic [2], there are the SATAx_TP, TN, RP, and RN CPU pins that are the actual SATA data, and SATAx_ACT and SATAx_PRESENT indicators that get mapped to GPIO pins.

To get at the indicators: SATA0_ACT can be mapped to GPIO pins 5, 11, 15, 21, or 35; SATA1_ACT can be mapped to GPIO pins 4, 10, 16, 20, or 34.  SATA0_PRESENT can be mapped to 9, 17, or 23.  SATA1_PRESENT can be mapped to 8, 14, or 22.  These pins are available on the 30-pin connectors.  Pins 12-17 go to the SD card on the daughterboard and could be grabbed there if you don't use the SD card.  Pins 20-23 don't go to the daughter card but have the advantage of not being otherwise used.

[1] http://www.marvell.com/files/products/embedded_processors/kirkwood/HW_88F6281_OpenSource.pdf
[2] http://www.plugcomputer.org/index.php/us/component/content/article/39-sch-and-bom/52-files

EDIT: I looked at the Gerber files, and apparently the SATA power and data pins on the CPU aren't wired to anything :-(
7  Hardware and U-Boot firmware / Hardware / Re: Loose mini-USB connector on: June 26, 2009, 11:40:37 PM
I got my SheevaPlug today, and immediately discovered I couldn't connect to the serial port.  The problem was a tragically loose mini-usb connector that comes undone if you touch it.  (This was a bit of a surprise since I'm used to cell phones that have excessively snug mini-usb connections.)  Pushing the plug in all the way and being very careful got it working.  It's interesting to see other people have this problem.
8  Hardware and U-Boot firmware / Hardware / Re: i2c and/or GPIO? on: June 15, 2009, 07:53:25 AM
I assume that if you use I2C (either bit-banged GPIO or via the TWSI pins), you'd need to use 3.3V devices since the Sheevaplug is 3.3V.  I expect that applying 5V to the Sheevaplug inputs would be a bad thing.   (Based on my reading of the datasheet, not experience.)
9  General Category / General Discussion / plugcomputer.org home page: bad links on: June 14, 2009, 03:59:43 PM
For the administrator of plugcomputer.org: All the links under the PLUGWIKI section of the home page http://plugcomputer.org seem to be broken.  E.g. the FAQ link: http://www.openplug.org/plugwiki/index.php?title=Frequently_Asked_Questionsdiff=863oldid=prev
The problem is the diff=863oldid=prev part.  It looks like whatever is generating these links is dropping the ampersands; the link should be ...Questions&diff=863&oldid=prev
10  Hardware and U-Boot firmware / Hardware / Re: i2c and/or GPIO? on: June 14, 2009, 03:24:03 PM
I've been looking at how to access the I2C /TWSI port.  According to the Hardware Specifications [1] p.53, the TW_SDA and TW_SCK can be mapped to the multi-purpose pins MPP8 and MPP9.  Unfortunately these pins are used for the UA_RTS and UA_CTS UART connection to the mini-USB.  (They appear in the schematic as connected to pin 23 and 23 on the 30-pin connectors.)

I think what you'd need to do to use this is change the MPP register setup in the kernel (however that's done) to map the TW functions to MPP8 and MPP9.   You wouldn't be able to use the development board, since those pins are connected to the USB chip.  Although maybe you could also direct UA_RTS and UA_CTS to MPP15 and MPP16, wire those pins to the USB chip, and then use both the mini-USB and TWSI.  (The mappings between the I/O functions and the 50 MPP pins is a bit confusing, as each pin can map to up to 8 different functions, and each function can map only to one or a few specific pins.  Examining the hardware specifications document will clarify this.)

My understanding from the schematic [2] is that MPP0-5 and MPP18-19 are used for NAND flash, MPP6 is used for reset, MPP7 is used for ?, MPP28-29 are used for USB power control, MPP33 is used for ?, and MPP49 is used for a LED.  The other MPP pins are available on the 30-pin connectors, but MPP8-11 are used for UART for the mini-USB, and MPP12-17 are used for the SD card.  This constrains what functions can be used on the remaining pins.  For instance, SPI requires some of the pins used by NAND flash, so it's not available.  It looks like the unused MPP pins are 20-27, 31-32, and 34-48.

(I should mention that I haven't tried any of this.)

[1] http://www.marvell.com/files/products/embedded_processors/kirkwood/HW_88F6281_OpenSource.pdf
[2] http://www.plugcomputer.org/index.php/us/component/content/article/39-sch-and-bom/52-files
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