Acurite 02032CAUDI Weather Station

I found an Acurite Weather Center 02032CAUDI at Costco for $99, which seemed like a pretty good deal.

It includes the "colour" display panel and a 5-in-1 remote sensor that includes temperature, wind-speed and direction, humidity and rain gauge.

The colour in the diplay is really just a fancy background sticker with the usual calculator-style liquid-crystal display in front. It does seem that for whatever reason the viewing angle is extremely limited; even off centre a little and it becomes very dim. It has an inbuilt backlight that is quite bright; it is either off or on (3-levels) or in "auto" mode, which dims it to the lowest level at certain hours. Hacking in a proximity sensor might be a fun project. The UI is OK; it shows indoor and outdoor temperature/humidity, wind-speed/rain and with is able to show you highs and lows with a bit of scrolling.

I was mostly interested in its USB output features. After a bit of fiddling I can confirm I've got it connected up to Meteobridge that is running on a Dlink DIR-505 and reporting to Weather Underground. One caveat is that you do need to plug the weather-station into a powered USB hub, rather than directly into the DIR-505; I believe because the DIR-505 can only talk directly to USB2.0 devices and not older 1.5 devices like the weather station. Another small issue is that the Meteobridge license is €65 which is not insignificant. Of course with some effort you can roll-your-own such as described in this series which is fun if you're looking for a project.

Luckily I had a mounting place that backed onto my small server cupboard, so I could easily run the cables through the wall to power and the DIR-505. Without this the cables might end up a bit of a mess. Combined with the fairly limited viewing angle afforded, finding somewhere practical to put the indoor unit might be one of the hardest problems.

Mounting the outdoor unit was fine, but mine is a little close to the roof-line so I'm not sure the wind-speed and direction are as accurate as if it were completely free-standing (I think official directions for wind-speed are something like free-standing 10m in the air). It needs to face north; both for the wind-direction and so the included solar-panel that draws air into the temp/humidity sensor is running as much as possible (it works without this, but it's more accurate with the fan). One thing is that it needs to mounted fairly level for the rain-gauge; it includes a small bubble-level on the top to confirm this. Firstly you'll probably find that most mount points you thought were straight actually aren't! Since the bubble is on the top, if you want to actually see it you need to be above it (obviously) which may not be possible if you're standing on a ladder and mounting it over your head. This may be a situation that inspires a very legitimate use of a selfie-stick.

It's a fun little device and fairly hackable for an overall reasonable price; I recommend.

On VMware and GPL

I do not believe any of the current reporting around the announced case has accurately described the issue; which I see as a much more subtle question of GPL use across API layers. Of course I don't know what the real issue is, because the case is sealed and I have no inside knowledge. I do have some knowledge of the vmkernel, however, and what I read does not match with what I know.

An overview of ESXi is shown below

overview of vmkernel and vmkapi

There is no question that ESXi uses a lot of Linux kernel code and drivers. The question as I see it is more around the interface. The vmkernel provides a well-described API known as vmkapi. You can write drivers directly to this API; indeed some do. You can download a SDK.

A lot of Linux code has been extracted into vmkLinux; this is a shim between Linux drivers and the vmkapi interface. The intent here is to provide an environment where almost unmodified Linux drivers can interface to the proprietary vmkernel. This means vendors don't have to write two drivers, they can re-use their Linux ones. Of course, large parts of various Linux sub-systems' API are embedded in here. But the intent is that this code is modified to communicate to the vmkernel via the exposed vmkapi layer. It is conceivable that you could write a vmkWindows or vmkOpenBSD and essentially provide a shim-wrapper for drivers from other operating systems too.

vmkLinux and all the drivers are GPL, and released as such. I do not think there could be any argument there. But they interface to vmkapi which, as stated, is an available API but part of the proprietary kernel. So, as I see it, this is a much more subtle question than "did VMware copy-paste a bunch of Linux code into their kernel". It goes to where the GPL crosses API boundaries and what is considered a derived work.

If nothing else, this enforcement increasing clarity around that point would be good for everyone I think.

Netgear CG3100D-2 investigation

The Netgear CG3100D-2 is the default cable-modem you get for Telstra Cable, at least at one time. Having retired it after changing service providers, I wanted to see if it was somewhat able to be re-purposed.

In short it's hackability is low.

First thing was to check out the Netgear Open Source page to see if the source had anything interesting. There is some source, but honestly when you dig into the platform code and see things like kernel/linux/arch/mips/bcm963xx/setup.c:

/***************************************************************************
 * C++ New and delete operator functions
 ***************************************************************************/

/* void *operator new(unsigned int sz) */
void *_Znwj(unsigned int sz)
{
    return( kmalloc(sz, GFP_KERNEL) );
}

/* void *operator new[](unsigned int sz)*/
void *_Znaj(unsigned int sz)
{
return( kmalloc(sz, GFP_KERNEL) );
}
...

there's a bit of a red-flag that this is not the cleanest code in the world (I guess it interfaces with some sort of cross-platform SDK written in some sort of C++).

So next we can open it up, where it turns out there are two separate UARTs as shown in the following image.

UART connections on Netgear CG3100D 2BPAUS

One of these is for the bootloader and eCOS environment, and the other seems to be connected to the Linux side.

A copy of the boot-logs for the bootloader and eCOS and Linux don't show anything particuarly interesting. The Linux boot does identify itself as Linux version 2.6.30-V2.06.05u while the available source lists its version as 2.6.30-1.0.5.83.mp2 so it's questionable if the source matches whatever firmware has made it onto the modem.

We do see that this identifies as a BCM338332 which seems to be one of the many sub-models of the BCM3383 SoC cable-modem solution. There is an OpenWrt wiki page that indicates support is limited.

Both Linux and eCos boot to a login prompt where all the usual default combinations of login/passwords fail. So my next thought was to try and get to the firmware via the bootloader, which has a simple interface

BCM338332 TP0 346890
Reset Switch - Low GPIO-18 50ms
MemSize:            128 M
Chip ID:     BCM3383G-B0

BootLoader Version: 2.4.0alpha14R6T Pre-release Gnu spiboot dual-flash reduced DDR drive linux
Build Date: Mar 24 2012
Build Time: 14:04:50
SPI flash ID 0x012018, size 16MB, block size 64KB, write buffer 256, flags 0x0
Dual flash detected.  Size is 32MB.
parameter offset is 49944

Signature/PID: a0e8


Image 1 Program Header:
   Signature: a0e8
     Control: 0005
   Major Rev: 0003
   Minor Rev: 0000
  Build Time: 2013/4/18 04:01:11 Z
 File Length: 3098751 bytes
Load Address: 80004000
    Filename: CG3100D_2BPAUS_V2.06.02u_130418.bin
         HCS: 1e83
         CRC: b95f4172

Found image 1 at offset 20000

Image 2 Program Header:
   Signature: a0e8
     Control: 0005
   Major Rev: 0003
   Minor Rev: 0000
  Build Time: 2013/10/17 02:33:29 Z
 File Length: 3098198 bytes
Load Address: 80004000
    Filename: CG3100D_2BPAUS_V2.06.05u_131017.bin
         HCS: 2277
         CRC: a6c0fd23

Found image 2 at offset 800000

Image 3 Program Header:
   Signature: a0e8
     Control: 0105
   Major Rev: 0002
   Minor Rev: 0017
  Build Time: 2013/10/17 02:22:30 Z
 File Length: 8277924 bytes
Load Address: 84010000
    Filename: CG3100D_2BPAUS_K2630V2.06.05u_131017.bin
         HCS: 157e
         CRC: 57bb0175

Found image 3 at offset 1000000

Enter '1', '2', or 'p' within 2 seconds or take default...
. .

Board IP Address  [0.0.0.0]:           192.168.2.10
Board IP Mask     [255.255.255.0]:
Board IP Gateway  [0.0.0.0]:
Board MAC Address [00:10:18:ff:ff:ff]:

Internal/External phy? (e/i/a)[a]
Switch detected: 53125
ProbePhy: Found PHY 0, MDIO on MAC 0, data on MAC 0
Using GMAC0, phy 0

Enet link up: 1G full


Main Menu:
==========
  b) Boot from flash
  g) Download and run from RAM
  d) Download and save to flash
  e) Erase flash sector
  m) Set mode
  s) Store bootloader parameters to flash
  i) Re-init ethernet
  p) Print flash partition map
  r) Read memory
  w) Write memory
  j) Jump to arbitrary address
  X) Erase all of flash except the bootloader
  z) Reset

Flash Partition information:

Name           Size           Offset
=====================================
bootloader   0x00010000     0x00000000
image1       0x007d0000     0x00020000
image2       0x007c0000     0x00800000
linux        0x00800000     0x01000000
linuxapps    0x00600000     0x01800000
permnv       0x00010000     0x00010000
dhtml        0x00200000     0x01e00000
dynnv        0x00040000     0x00fc0000
vennv        0x00010000     0x007f0000

The "read memory" seems to give you one byte at a time and I'm not certain it actually works. So I think the next step is solder some leads to dump out the firmware from the flash-chip directly, which is on the underside of the board. At that point, I imagine the passwords would be easily found in the image and you might then be able to leverage this into some sort of further hackability.

If you want a challenge and have a lot of time on your hands, this might be your platform — but practically I think the best place for this is the recycling bin.

rstdiary

I find it very useful to spend 5 minutes a day to keep a small log of what was worked on, major bugs or reviews and a general small status report. It makes rolling up into a bigger status report easier when required, or handy as a reference before you go into meetings etc.

I was happily using an etherpad page until I couldn't save any more revisions and the page got too long and started giving javascript timeouts. For a replacement I wanted a single file as input with no boilerplate to aid in back-referencing and adding entries quickly. It should be formatted to be future-proof, as well as being emacs, makefile and git friendly. Output should be web-based so I can refer to it easily and point people at it when required, but it just has to be rsynced to public_html with zero setup.

rstdiary will take a flat RST based input file and chunk it into some reasonable looking static-HTML that looks something like this. It's split by month with some minimal navigation. Copy the output directory somewhere and it is done.

It might also serve as a small example of parsing and converting RST nodes where it does the chunking; unfortunately the official documentation on that is "to be completed" and I couldn't find anything like a canonical example, so I gathered what I could from looking at the source of the transformation stuff. As the license says, the software is provided "as is" without warranty!

So if you've been thinking "I should keep a short daily journal in a flat-file and publish it to a web-server but I can't find any software to do just that" you now have one less excuse.

Bash arithmetic evaluation and errexit trap

In the "traps for new players" category:

count=0
things="0 1 0 0 1"

for i in $things;
do
   if [ $i == "1" ]; then
       (( count++ ))
   fi
done

echo "Count is ${count}"

Looks fine? I've probably written this many times. There's a small gotcha:

((expression))
The expression is evaluated according to the rules described below under ARITHMETIC EVALUATION. If the value of the expression is non-zero, the return status is 0; otherwise the return status is 1. This is exactly equivalent to let "expression".

When you run this script with -e or enable errexit -- probably because the script has become too big to be reliable without it -- count++ is going to return 0 (post-increment) and per above stop the script. A definite trap to watch out for!

Finding out if you're a Rackspace instance

Different hosting providers do things slightly differently, so it's sometimes handy to be able to figure out where you are. Rackspace is based on Xen and their provided images should include the xenstore-ls command available. xenstore-ls vm-data will give you a handy provider and even region fields to let you know where you are.

function is_rackspace {
  if [ ! -f /usr/bin/xenstore-ls ]; then
      return 1
  fi

  /usr/bin/xenstore-ls vm-data | grep -q "Rackspace"
}

if is_rackspace; then
  echo "I am on Rackspace"
fi

Other reading about how this works:

ip link up versus status UP

ip link show has an up filter which the man page describes as display running interfaces. The output also shows the state, e.g.

$ ip link
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default
  link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
  link/ether e8:03:9a:b6:46:b3 brd ff:ff:ff:ff:ff:ff
3: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DORMANT group default qlen 1000
  link/ether c4:85:08:2a:6e:3a brd ff:ff:ff:ff:ff:ff

It is not described what the difference is between these two.

The state output is derived from IFLA_OPERSTATE as per this little bit in ip/ipaddress.c in iproute2

if (tb[IFLA_OPERSTATE])
  print_operstate(fp, rta_getattr_u8(tb[IFLA_OPERSTATE]));

as per operstates.txt a status of UP means that the interface is up and can be used to send packets.

In contrast, ip link show up runs a different filter

if (filter.up && !(ifi->ifi_flags&IFF_UP))
  return 0;

Thus only interfaces that are in state IFF_UP are shown. This means it is administratively up, but this does not mean it is available and ready to send packets.

This may make a difference if you're trying to use the output of ip link in any sort of automation where you have to probe the available network-interfaces and know where packets are going to get out or not.

Non-stick tortilla technique

I have never had much success with tortilla making, generally finding the fragile masa would stick to everything and tear easily. However I was listening to the Cook's Illustrated podcast where they mentioned that cooking a pizza on a stone with silicone-paper makes no difference over doing it on the stone directly. For some reason I had just never thought of cooking it with the silicone-paper on; I'd always frustrated myself trying to separate the pressed tortilla in various ways.

So here's my technique:

  1. Mix the masa as on the packet; 2 cups to 2-half cups water
  2. Leave for 20 minutes or so
  3. Use plastic-wrap on the top of the tortilla press
  4. Cut a silicone-paper square for the bottom
  5. Ball the masa and press
  6. Now the plastic-wrap will peel easily off the top of the uncooked tortilla
  7. Take the silcone-paper and put the tortilla down on the pan/hotplate
  8. Give a slight press with the spatula around the edges
  9. After about 20 seconds, the silicone-paper should peel off the tortilla fairly easily.
  10. repeat!

I've tried mixing in suet, oil and copha and none of them are worth the extra calories over just plain masa in my opinion and don't help with sticking anyway. Enjoy!