Difference between revisions of "DHT-Walnut-Flameman"

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==== The J5 Header ====
==== The J5 Header ====
The J5 header located to the left of the RAM slot actually has 9 GPIO pins wired to it. [[GPIOs]] 1 to 9 to be exact. That header also has the Power and Media [[LEDs]] wired to it, so using the first 2 pins will look awkward if your bit-banging to say a SD/MMC card or LCD display. The J5 header has the following layout. As things are developed they will be added.
The J5 header located to the left of the RAM slot actually has 9 GPIO pins wired to it. [[GPIOs]] 1 to 9 to be exact. That header also has the Power and Media [[LED|LEDs]] wired to it, so using the first 2 pins will look awkward if your bit-banging to say a SD/MMC card or LCD display. The J5 header has the following layout. As things are developed they will be added.

Revision as of 12:02, 24 September 2007


please note this page is actively being updated, it is merged from the old version of wiki. so keep patient, i will rewrite this documentation as soon as possible

in case you need a pdf copy of the old doc, or if you need attachments feel free to ask me for them ( speeder@alice.it )


The Target-goal of this page is

  • install gentoo-ppc32 into harddisk
  • make the board able to boot from it
  • describe how to build a jtag cable (to debug and recover from "Brickage")
  • describe something useful with you can do with the board
  • describe other Operating System avalaible for the board

logical steps about installing gentoo

  • add the JTAG connector at J10 (you could skip it, it is suggested)
  • build the JTAG cable (you could skip it, it is suggested))
  • replace the bootloader with ppcboot 1.1.6/U-boot 1.1.4
  • make partitions on the Hard Disk
  • populate them
  • set the bootloader environment to book from the Hard Disk

People you could contact if you need help

  • people on irc freenode #edev #mklinux may be asked about
  • flameman, i'm currently use this board for an university project running gentoo-ppc, email speeder@alice.it
  • you ... if you want ;-)

i need to ask these people if they could be reported to be contacted

  • dale-elinux@farnsworth.org
  • GPSfan (irc freenode)
  • Prpplague (irc freenode), Email: danders AT SPAMFREE amltd DOT com

About the board

DHT-Walnut is a shortened name for the Digital Home Technologies PCB 01070201 Rev. 1.1.

The DHT-Walnut board is based on the AMCC-Walnut (still available, and still expensive :P). It is a more improved board described at www.amcc.com.

A "walnut" searching will inform about schematic and software.

Also keep attention @ DENX: they have developed a lot for the AMCC-Walnut board, and you could find a linux patch for your problem, prettier documentation, developer suit, and much more: in case, you are suggested to have a look to their web pages.

you could find it on ebay, search for "walnut", or "powerpc"

MIND UP the differences between "DHT WALNUT" and "AMCC WALNUT" (ALSO CALLED "IBM WALNUT")


The board consists of:

  • CPU PowerPC 405GP running at 266mhz
  • RAM PC133 SDRAM slot, currently, only supports single sidded DIMMs
  • LAN On-chip 405GP ethernet, board doesn't have an ethernet MAC address (the monitor/bootloader is able to fix it)
  • UART DCE serial port, speeds up to 230k, only tested to 115200bps
  • PCI two pci slots, keyed for 5V only cards
  • IDE Promise Technologies PDC20265 IDE
  • ROM 512k of boot flash, AMD 29LV040B (amd29lv040b.pdf), soldered on the PCB, if you like to use a socket you have to consider the bootloader will check for the flash manufactor ID, so or you replace the 29LV040B with an other socked-29LV040B, or you have to modify the bootloader
  • POWER the board need to be 12v dc powered 2A max, it is able to feed the hard disk
  • System PCB 6.00" x 7.5" board size
  • RTC the real time clock chip is missing
  • RAM 32M PC133 SDRAM DIMM, the board has issues with more than 128M: if you inspect the pcb, you will see that the DIMM connector has same pin missing, this is the reason why you can't use DIMM bigger than 128M
  • PCI IEEE-1394 card supported by OHCI driver
  • PCI additional ethernet board needed cause the on board ethernet is implemented by the IBM-ppc-405GP, for example netbsd is not able to drive it, so in case you need an additional board, the one provided with DHT is good enough
  • FIRMWARE PPCBoot v.1.1.2 in flash (it has issues with environment, it need to be replaced with a gooder one)

Memory Locations

memory map of the board will be added as soon as possible

addr begin addr end area
40000 ?? ram, userspace
400000 ?? ram, userspace
0xef600700 0xef600700+4 PPC405GP, GPIO output register
0xef600704 0xef600704+4 PPC405GP, GPIO Tri-State register, Controls if pin is active when high.
0xef600718 0xef600718+4 PPC405GP, GPIO Open Drain register. Controls if pin is an open drain or active output.
0xef60071c 0xef60071c+4 PPC405GP, GPIO Input register. synchronized with OPBClk
0xfff80000 ??? ???
0xfffa0000 0xfffaffff flash, bootloader data
0xfffb0000 0xfffbffff flash, bootloader data
0xfffc0000 0xffffffff flash, bootloader
0xfffffffc 0xfffffffc+4 flash, PPC405GP boots from this location ???

Open questions

1) how/where is ram mapped ?

2) how/where is harddisk mapped ?

3) how/where is pci mapped ?

3) what is the bootstrap addr of the flash ?

the u-boot image "sits" at the end of the flash, the 4xx PPC's boot from location 0xfffffffc, so the bootloader needs to be located at the end, so if u-boot is 256kbyte then it is located 0xfffc0000 ... 0xffffffff

the dht-walnut flash memory mapped, it's mapped via the 405gp EBC (external bus controller)



  • uboot has issues in PCI/DMA initialization. More will be post in the future
i found a problem using a pci sound card in the DHT-WALNUT.
It has been correctly recognized by the kernel, the DMA feature (ppc405-dma) is setted, but the card is not working.

somebody says it is a bug, somebody says ppcboot solves the problem inizializing the pci in the correct way. I don't know, i'm using the uboot v1.1.4 and it is not working

also have a look to this

<> but i already thought so when i saw the "pci long" output
<> no BAR was assigned with an address
<> this was different some time ago
<> could be something changed in the last few months in the common pci support
<> i'll check with an ex-kollegue and let you know
<> this will take till beginning of next week though
<> hey, i just checked the source (sometimes helpful)
<> you just need to enable the host bridge configuration via an env variable
<> => setenv pciconfighost yes
<> then
<> => saveenv
<> => reset
<> after this reset the BAR1 will be configured:
<> => pci long
<> Scanning PCI devices on bus 0
<> Found PCI device 00.00.00:
<>   vendor ID =                   0x1014
<>   device ID =                   0x0156
<>   command register =            0x0006
<>   status register =             0x2210
<>   revision ID =                 0x01
<>   class code =                  0x0b (Processor)
<>   sub class code =              0x20
<>   programming interface =       0x00
<>   cache line =                  0x00
<>   latency time =                0x87
<>   header type =                 0x00
<>   BIST =                        0x00
<>   base address 0 =              0x00000000
<>   base address 1 =              0x80000008

could you help me to understand how to plug a soundcard ?

Images of the board


see more detailed photo dht-walnut-ppc405-top


The BEST solution is to equip your lab with the bdi2000. This hardware is expensive a lot, 'cause it is not a simple download cable, it's a professional debugger

For this dht-walnut project it has been used "OCD Commander is macraigor's free debugger software", that i'm going to illustrate

JTAG & OCD Commander

The OCD Commander is macraigor's free debugger software, which allows you to connect to your supported target type chip via the On-Chip Debug port (BDM or JTAG) using a Macraigor hardware device. You will be able to test the connection, memory access, modify memory and registers, run code and more using this product. This debugger is not designed to be used to program flash devices connected to your target. The OCD Commander software is supported under Windows 98/ME, NT, 2000, 2003, XP operating systems

supported devices

  • mpDemon
  • Raven
  • wiggle <------- it will be illustrated
  • usb2demon
  • usb2sprite
  • usbwiggler

See How To build the JTAG Wiggle interface & add the JTAG connector at J10, Just in case you make a brick, you could fix the jam, using this procedure: JTAG Bootloader Installation

JTAG add the J10 to the board


To add the J10 to the board suck or wick the solder out of the holes and solder it in, but be minded a common header has pins larger than holes, so ... be careful about what you do: you could damage the PCB




  • DHT-Walnut: JTAG Pin Out Connector Specifications for DHT-walnut-PPC405GP
  • AMCC-PPC4xx: JTAG Pin Out Connector Specifications for AMCC PPC 44X, 40X (4XX) Processors: 405EP, 405GP, 405GPR, 440GP, 440EP, 440GX, 440GR, 440EPX, 440GRX, 440SP, 440SPE

02 nc nc
05 *NC* *NC*
06 Vcc Vcc
08 nc KSTP_IN
10 nc nc
12 nc nc
14 nc reserved
16 gnd gnd

Pin Out description

  • TDO=JTAG Test Data Out
  • TDI=JTAG Test Data In
  • TRST=JTAG Test Reset
  • TCK=JTAG Test Clock
  • TMS=JTAG Test Mode Select
  • *NC*=not connected, used as cable reference
  • nc=simply not connected
  • SRESET=Soft-Reset
  • HRESET=Hard-Reset
  • KSTP_OUT=?
  • CKSTP_IN=?
  • Vcc=board ref voltage, 3V

About the software for the jtag cable

from http://www.macraigor.com/cpus.htm and you can download the OCD-commander, but it will not work with the wiggle

  • 'cause in the new OCD-commander AMCC PowerPC PPC405 wiggler is NOT supported
  • 'cause in the new OCD-commander IBM PowerPC PPC 405 wiggler is NOT supported

you need to download this old version, that i tested with success under windows2000 OCD-Commander-for-wiggle.zip

JTAG build the Wiggle Cable

the the "Wiggler Buffered JTAG Programmer" is compatible with the old OCD. This schematic has been tested and it is working.



OCD, Experimental hack

Experimental hack to set a hardware breakpoint inside OCD Commander [media:hardbreak.tgz]

  • OCD Commander macro file to dump the CPU configuration (all but PCI) [media:dump_config.mac]
  • OCD Commander macro file to configure the system for recovery attachment:recovery_config.mac]
  • CPU configuration of the system after a warm reset [media:warm_reset.config]
  • CPU configuration of the system once ppcboot v1.1.2 is up and running [media:ppcboot.config]
  • CPU configuration of the system once ppcboot v1.1.6 is up and running [media:ppcboot_116.config]
  • Example OCD logfile of the using the recovery macro to load ppcboot [media:ocd_recovery_log.txt]
  • Example console log from ppcboot v.1.1.6 running from ram after recovery macro [media:ocd_recovery_console_log.txt]

OCD, Recovering a bricked board

Using OCD Commander, a JTAG adapter, and GPSFan's ram resident ppcboot, it is possible to reprogram the flash. In short, use OCD Commander to turn on the sdram, download the ram targeted ppcboot, and install a new bootloader.

You'll need a macro file recovery_config.mac and the ppcboot image ppcboot_ram.srec .

There's also an experimental ram-resident version of u-boot-1.1.4 attachment:u-boot-ram.s19 that can be downloaded to 0x400000. Source diffs against the current version from CVS, incorporating the patches from both GPSFan and dfarnsworth: attachment:u-boot-ram.patch . Expect to see much more output at boot, as this version has debug output turned on. (Other changes include setting the entry point in the linker script, output files renamed to u-boot.s19 and u-boot.elf, sdram config disabled, added debug info on code relocation, and a modified default environment.)

  • Start OCD Commander, connect to the board, reset, and halt.
  • reset
  • The CPU should be ready to fetch the first instruction:
  • cpu
* PC: FFFFFFFC    CR: 00000000  MSR: 00000000  LR: 01FD327C
* B  -524028
  • Configure the system:
  • recovery_config (Or hit the macro button and navigate to the recovery_config.mac file.)
  • endian big (BIG Endian set for WORD and DASM commands)
  • Download the ppcboot image to ram:
  • down
* ppcboot_ram.s19: downloaded 163100 bytes in 0 minutes, 22.785 seconds
* PC set to starting address 0x00400000
  • Jump to the startup (which isn't the same as the download address):
  • go 0x400100

At this point, you should have a running ppcboot v1.1.6. Install a new flash resident bootloader using the bootloader update procedure Installing the Updated Bootloader


* ppcboot 
* U-Boot

U-Boot 1.1.4

It is a significantly updated replacement for ppcboot. U-Boot for the DHT-Walnut DENX U-Boot and Linux Guide for Walnut

Changes since u-boot-1.1.4-df1.bin:

  • A default ethaddr is now set: de:ad:be:ef:00:00
  • The ethaddr can be changed as often as you like. Use: setenv ethaddr be:ef:be:ef:be:ef ; saveenv
  • Only the first two memory banks of a DIMM are used. This allows us to use (half of) double-sided DIMMS.

Some things to note when changing from ppcboot to U-Boot:

  • Default baudrate is 115200.
  • Occupies flash addresses 0xfffc0000-0xffffffff
  • Maintains two copies of environment data, primary copy at 0xfffb0000, backup copy at 0xfffa0000.


  • Boot the board and bring it to the ppcboot (or U-Boot) console prompt.
  • Download the new bootloader [[Media:u-boot-1.1.4-df2.bin]u-boot-1.1.4-df2.bin]] into RAM:

(1) Using Kermit (you'll need a terminal emulator that supports the kermit file transfer mode): loadb 800000 115200

  • Switch baudrate to 115200 bps and press ENTER ...
  • Ready for binary (kermit) download ...
  • Start Addr=0x00800000
  • Switch baudrate to 9600 bps and press ESC ...

(2) Using tftpboot (requires a tftp server and setting the environment variables ethaddr, ipaddr and serverip)

  • tftpboot 800000 u-boot-1.1.4-df2.bin Using ppc_4xx_eth0 device
* TFTP from server; our IP address is
* Filename 'u-boot.bin'.
* Load address: 0x800000
* Loading: done
* Bytes transferred = 262144 (40000 hex)
  • Verify that the download was received correctly (crc should be 0xd3cef189):
  • crc 800000 40000
  • CRC32 for 00800000 ... 0083ffff ==> d3cef189
  • Unprotect the last 4 sectors:
  • protect off fffc0000 ffffffff
  • Un-Protected 4 sectors

From this point on, do *not* power down the board, and type *very* carefully. This is the critical section.

  • Erase the last four sectors:
  • erase fffc0000 ffffffff
* Erase Flash from 0xfffc0000 to 0xffffffff
* Erasing sector fffc0000
* Erasing sector fffd0000
* Erasing sector fffe0000
* Erasing sector ffff0000
* done
* Erased 4 sectors
  • Copy the new bootloader into flash:
  • cp.b 800000 fffc0000 40000
* Copy to Flash... done
  • Verify that the image is correct (crc of u-boot-1.1.4-df2.bin is 0xd3cef189).
  • crc fffc0000 40000
* CRC32 for fffc0000 ... ffffffff ==> d3cef189

End of critical section. Congratulations!

  • Reset the board and see that the new version booted!
  • Don't forget to change your baud rate to 115200!
  • reset

You will see a message like : *** Warning - bad CRC, using default environment. That's normal. It will go away after you issue a saveenv command.

ppcboot 1.1.6

the latest ported ppcboot is 1.1.6, it need a patch and it will build for flashing at 0xfff80000 as a replacement for the pcboot-1.1.2 that comes with the board.


Quick notes on installing ppcboot v1.1.6.1

  • Boot the board and bring it to the ppcboot console prompt.
  • Check current flash configuration:

=> flinfo

Bank # 1: AMD AM29F040 (512 Kbit, uniform sector size)
  Size: 512 KB in 8 Sectors
  Sector Start Addresses:
    FFF80000  RO  FFF90000  RO  FFFA0000  RO  FFFB0000      FFFC0000
    FFFD0000      FFFE0000      FFFF0000     

Note that the bottom three sectors, containing the existing 1.1.2 bootloader, are protected. We also want to protect the last sector, which contains the initial jump instruction, so:

=> protect on ffff0000 ffffffff

Protected 1 sectors
  • Zero out a section of ram before the download:

=> mw.b 400000 0 30000

  • Now download the new bootloader ppcboot1.1.6.1.bin into ram (you'll need a terminal emulator that supports the kermit file transfer mode):

=> loadb 400000 115200

## Switch baudrate to 115200 bps and press ENTER ...
## Ready for binary (kermit) download ...
## Start Addr      = 0x00400000
## Switch baudrate to 9600 bps and press ESC ...
  • Verify that the download was received correctly (crc should be 0x083fb0a3):

=> crc 400000 30000

CRC32 for 00400000 ... 0042ffff ==> 083fb0a3
  • Erase the three spare sectors, which we'll use to backup the 1.1.2 bootloader:

=> erase fffc0000 fffeffff

Erase Flash from 0xfffc0000 to 0xfffeffff
Erasing sector fffc0000
.Erasing sector fffd0000
.Erasing sector fffe0000
. done
Erased 3 sectors
  • (Optional: erase the 0xfffb0000 sector, which will be used for non-volatile environment storage.)

=> erase fffb0000 fffbffff

Erase Flash from 0xfffb0000 to 0xfffbffff
Erasing sector fffb0000
. done
Erased 1 sectors
  • Check that sectors 0xfffc0000 to 0xfffe0000 are erased, and sector 0xffff0000 is protected:

=> flinfo

Bank # 1: AMD AM29F040 (512 Kbit, uniform sector size)
  Size: 512 KB in 8 Sectors
  Sector Start Addresses:
    FFF80000  RO  FFF90000  RO  FFFA0000  RO  FFFB0000 E    FFFC0000 E
    FFFD0000 E    FFFE0000 E    FFFF0000  RO 
  • Now we're ready to backup the 1.1.2 bootloader. Copy three sectors from 0xfff80000 to 0xfffc0000:

=> cp.b fff80000 fffc0000 30000

Copy to Flash... done
  • Easy enough, right? Compare just to be sure it went ok:

=> cmp.b fff80000 fffc0000 30000

Total of 196608 bytes were the same
  • Now we're ready to modify the bootsectors. We'll turn off protection, erase the three bottom sectors, and copy the new bootloader from ram.
  • Unprotect the bottom three sectors:

=> protect off fff80000 fffaffff

Un-Protected 3 sectors

From this point on, do *not* power down the board. This is the critical section.

  • Erase the bottom three sectors with the original 1.1.2 bootloader:

=> erase fff80000 fffaffff

Erase Flash from 0xfff80000 to 0xfffaffff
Erasing sector fff80000
.Erasing sector fff90000
.Erasing sector fffa0000
. done
Erased 3 sectors
  • Copy the new bootloader into flash:

=> cp.b 400000 fff80000 30000

Copy to Flash... done
  • Verify the copy:

=> cmp.b 400000 fff80000 30000

Total of 196608 bytes were the same
  • Verify that the image is correct (crc of ppcboot1.1.6.1.bin is 0x083fb0a3).

=> crc fff80000 30000

CRC32 for fff80000 ... fffaffff ==> 083fb0a3

End of critical section. Congratulations'

  • We've finished modifying flash, so turn the write protection back on:

=> protect on fff80000 fffaffff

Protected 3 sectors
  • Reset the board and see that the new version booted

=> reset

PPCBoot 1.1.6 (Feb  5 2006 - 21:38:51)

CPU:   IBM PowerPC 405GP Rev. E at 266.640 MHz (PLB=66, OPB=33, EBC=33 MHz)
           PCI async ext clock used, internal PCI arbiter enabled
           16 kB I-Cache 8 kB D-Cache

To sum up, you'll end up executing these commands:

=> protect on ffff0000 ffffffff

=> mw.b 400000 0 30000

=> loadb 400000 115200

=> crc 400000 30000

=> erase fffc0000 fffeffff

=> cp.b fff80000 fffc0000 30000

=> cmp.b fff80000 fffc0000 30000

=> protect off fff80000 fffaffff

=> erase fff80000 fffaffff

=> cp.b 400000 fff80000 30000

=> cmp.b 400000 fff80000 30000

=> crc fff80000 30000

=> protect on fff80000 fffaffff

boot from the tftp

It's relative easy if you have a tftp server setup

Have a kernel Image and Userland Image in the /tftpboot/ directory on your server =>tftpboot 400000 Working Kernel Image < kernel image loads > =>tftpboot c00000 Working Userland Image < userland image loads > bootm 400000 c00000 < kernel boots and loads userland image >


what you need

updating ...

you need

  • a PC running linux
  • an empty harddisk of 2..4Gbyte


  • put the dht-walnut harddisk into PC ide slot
  • partition the harddisk
  • install all the gentoo portages
  • remove the harddisk and put it into dht-walnut ide slot


updting ...


updating ..


Operating System available for this board


  • Netbsd has a port for "IBM PowerPC 405GP based Walnut evaluation board", this is not the DHT-Walnut, this is an other way to call the AMCC-Walnut (yes just to be confusing). Ok, it is not for DHT-Walnut, but this port could be (easealy / hardly) adapted to the DHT-Walnut with some work / over work

Hardware that is known to work with

  • see netbsd web, the hw could be (easealy / hardly) adapted to the DHT-Walnut with some work / over work


Linux Gentoo PPC32

  • Version 2.4 (Mostly) working kernel binary and config from jbevren with matrox fbcon and usb input support. Current issues: USB keyboard input doesnt seem to work, but events reach /dev/input/event0
  • Version 2.6 working

boot from HD

Work In Progress

ppcboot/U-Boot provides only basic functionality to access Hard disks: you can print the partition table and read and write blocks (addressed by absolute block number), but there is no support to create new partitions or to read files from any type of filesystem. The current version of ppcboot-1.1.6 has a problem with writing to hdd, however, once the Linux kernel is loaded and the userland initialized, the hdd can be accesses normally through PIO and DMA modes. This may or may-not be fixed in the future.

As usual, you can get some information about the available IDE commands using the help command in ppcboot:

  => help ide      
ide reset - reset IDE controller
ide info  - show available IDE devices
ide device [dev] - show or set current device
ide part [dev] - print partition table of one or all IDE devices
ide read  addr blk# cnt
ide write addr blk# cnt - read/write `cnt' blocks starting at block `blk#'
    to/from memory address `addr' 

You may create the needed partitions by tftpbooting Linux and an appropriate userland, then use fdisk to partition the disk. Then reboot back to ppcboot.

ppcboot can be configured for DOS and Mac OS? type partition tables. Since ppcboot cannot read files from a filesystem you should create one (or more) small partitions (maybe 1 or 2 MB) if you want to boot from the "disk". (The size of these partitions will depend on how large your kernel and userland images are)

You should create the following partiton table:

 # fdisk /dev/hdx
 hde: hdx1 hdx2 hdx3 hdx4

/dev/hde1  ID=83   Linux <---- 2Mb, boot kernel, dd if=kernel of=here
/dev/hde2  ID=83   Linux
/dev/hde3  ID=83   Linux <----  root & usr
/dev/hde4  ID=82   Swap  <---- 32Mb, swap

You should also initialized /dev/hdx4 as swap space.
# mkswap /dev/hdx4
Setting up swapspace

check how ppcboot/U-Boot will recognize this partition table:
<pre> => ide part

* dd if=kernel.img of=/dev/hdx1

To boot from a disk you can use the diskboot command:

<pre> => help diskboot
diskboot loadAddr dev:part 

The diskboot command expects a load address in RAM, and a combination of device and partition numbers, separated by a colon. It then reads the image from disk and stores it in memory. We can now boot it using the bootm command [to automatically boot the image define the ppcboot environment autostart with the value =yes=].

 => diskboot 400000 0:1
ide_read dev 0 start 0, blocks 1 buffer at 3F9F8C0
## Valid DOS partition found ##

Loading from IDE device 0, partition 1: Name: hda1
  Type: PPCBoot
First Block: 63,  # of blocks: 8001, Block Size: 512
ide_read dev 0 start 3F, blocks 1 buffer at 400000
   Image Name:   DHT Kernel

=> bootm 400000 c00000
## Booting image at 00400000 ...
   Image Name:   DHT Walnut Kernel
   Image Type:   PowerPC Linux Kernel Image (gzip compressed)

=> setenv bootargs root=/dev/ram0
=> setenv autostart yes
=> disk 400000 0:1 \;\ diskboot c00000 0:2 \;\ bootm 400000 c00000
=> bootd

(i will post all my setenv)

The above procedure puts the userland image from the second partition into a ramdisk. If you would like the userland to be an ext2/3/rieser/xfs partition on the hdd do the following:

  • make the partiton table as above
  • put the kernel and small userland onto the first partitions as above
  • populate the root&usr partition with the appropriate files (gentoo-ppc32 distro)
  • change bootargs to "bootargs root=/def/hda3"
  • bootd to try out the new root, if it works ok, reboot back to ppcboot, change the bootargs again and saveenv
  • bootd and enjoy your new system.

Hardware that is known to work with

There is a list of the Hardware that is known to work (and not to work) with this board. Feel free to add, comment, feedback about it.

  • matrox millennium I/II
  • 3com-netcard
  • ...

Compile from sources

Linux 2.6 has issues in the source's tree: the dht-Walnut has been originally ported to arch=ppc, while the new kernel tree is around arch=powerpcc, for this reason you need to specify the right arch or your compiler will have issues. Developers will port everything to arch=powerppc in the future. Kernel 2.6.12 is free of this problem, newer than .12 have it.

Driver, Control the Green Media LED and J5


The GPIO registers are quite fickle things. Not only are they for the Media LED and J5 header, they also manage the IRQs and Peripheral Chip selects. Hitting a wrong bit in Linux will cause problems, kernel panics, total lockups, bad things, 'plagues of locusts', you get the idea. When using the PPC405 _gpio driver below(or the 405_ocp_gpio driver in DENX Linux PPC 2.4, use a mask of 0xFFC00000, that way you don't manage to hit something you really don't want to.

Playing with the Media LED

The Media LED on the DHT-Walnut is wired to the processor by the GPIO pins. However its behind a 74VHC14 Schmitt Inverter. So you have to send it low in order to turn it on. This top section only covers the Media LED and the U-Boot/PPCBoot ROM Monitor.

Memory Locations

0xef600700 is the memory location of the GPIO output register. It's 4 bytes wide. It turns on and off the GPIO pins on the PPC405GP.

0xef600704 is the location of the Tri-State register. Also 4 bytes wide. Controls if the GPIO pin is active when high.

0xef600718 is the location of the Open Drain register. Also 4 bytes wide. Controls if the GPIO pin is an open drain or active output.

0xef60071c is the location of the GPIO Input register. Also 4 bytes wide. The state of each pin is reflected in the correspondig value in this register. (synchronized with OPBClk)

Playing with the LED

By having all the bits in the Tri-State register high and the Output register all low, The pins are driven low. Because the Media LED is behind the inverter it glows when low. Setting it high in the Output register will turn it off.

Example using U-Boot 1.1.4

Setting the Tri-State Register to drive all usable GPIOs.

=> nm 0xef600704
ef600704: 00000000 ? ffc00000
ef600704: ffc00000 ?

The LED should be lit now as its pin is driven low.

Turning the LED on and off with the Output Register

=> nm 0xef600700
ef600700: 00000000 ? 20000000  //LED should be off.
ef600700: 20000000 ? 00000000  //LED goes on.
ef600700: 00000000 ?

The J5 Header

The J5 header located to the left of the RAM slot actually has 9 GPIO pins wired to it. GPIOs 1 to 9 to be exact. That header also has the Power and Media LEDs wired to it, so using the first 2 pins will look awkward if your bit-banging to say a SD/MMC card or LCD display. The J5 header has the following layout. As things are developed they will be added.


pin addr function
GPIO3 0x100 I/O
GPIO4 0x080 I/O
GPIO5 0x040 I/O
GPIO6 0x020 I/O
GPIO7 0x010 I/O
GPIO8 0x008 I/O
GPIO9 none GND

Linux and the GPIOs

Module for 2.6.16

Using a module from a Monta Vista 2.4 kernel, I did the slight editing so that it will compile with 2.6.16. I have made a patch file that can be applied to a vanilla 2.6.16 kernel.

Also included is a small bit of test code to show how to operate the gpio driver.

Module patch and test code here: Media:ppc405_gpio.tar.gz

(Version 2 will be up once I clean some little problems out of the test code, possibly tonight)

Any errors or things you want to see, don't hesitate to let me know. I'll be slowly adding little things to the module as helpers.

Once you have your module installed and modprobe/insmoded, just run 'make' to built the test app. If you don't have a /dev/ entry yet just 'make dev' and it'll do it for you. DevFS isn't supported yet, I'm working on that now.

Project: do something useful with the board

DHT-Walnut as N.A.S.


I turned a DHT-Walnut + 300Gb hard disk into a file server to have my data files connected and shared to the LAN (Local Area Network).

N.A.S. stands for Network Attached Storage. They are storage devices attached to the lan. A NAS should be able to be connected to every kind of network. It should use both the access protocols NFS (Network File System) and CIFS (Common Internet File System)

I only enabled NFS service in the kernel configure because i don't need CIFS. UNIX servers use NFS, while Microsoft systems use CIFS, fortunately i don't have any Microsoft systems here :P Gentoo is installed in the first little partition of the hard disk (it is PC-partition style, so you can only have 4 partitions). It runs openssh, telnet, ftp, tftp, and NFS. As the fact there is no RTC chip installed i added special /etc/init.d/clock-sync to set the local time. The scrips uses rdata to retrieve the current time of an other machine.

In the photo you could see the case i realized: the hard drive is connected to the opened door, the DHT-walnut PCD has been placed inside, the green LED has been used to the frontal case to say "the booting has been completed, the system is ready" (used the gpio hack provided in patches for the 2.6.16-rc3). The black platform is from sony playstation2 and is is only a nice way to have the case vertically seated.

Don't keep about the ALS4000 pci sound board plugged in the upper PCI bus. It has been plugged just to use the NAS as the giant (300Gb) ipod you have ever seen .... but this is an other story ....

DHT-Walnut as MP3-player

Following in the footsteps of Nate True, I turned a DHT-Walnut + parts into a server to play my music collection. It grabs the data via nfs from an NSLU2, and is controlled via various mpc-like clients from my desktops.

mpd server


After the above was running flawlessly for a day, somehow the usb audio device got fried. May have been a ground loop in the stereo. I had gotten used to having music playing. so I dug out an old PCI sound card (CS4280 based) and compiled the drivers and plugged it in. GIGO... seems like IBM4xx DMA support needs to be turned on in the kernel to make it work. Things are fine now with a few extra ground wires, just to be sure.

Note: to use a PCI-sound card you need to use ppcboot. U-boot-1.1.6 has an issue with kernel initialization. It is under fixing, but today it causes the DMA not to work correctly with the sound card. No sound at all.