Cisco CP-7912 IP Phone

Cisco CP7912
I acquired a couple of Cisco CP-7912 IP Phones to take apart and see how they work, because around here, we love old, broken hardware to learn from and experiment with.

The Cisco 7912 usually runs SCCP (Skinny Call Control Protocol) and is not very useful for our purposes because we run Asterisk with SIP based hardware.

After googling for a bit, I found SIP firmware for this model phone, CP7912080001SIP060412A.ZIP on Cisco’s site, but you need an account with them to download the file. If you don’t have an account, try googling the file name.

The firmware will be loaded from a TFTP server when it boots, so you will need to extract the zip file and place the 3 files from the zip file into the TFTP root folder. The files you need are:


Then you will need to set the TFTP servers IP address in the phone. There are 2 ways to do this, 1) set option 66 in the DHCP server, 2) set in phones network configuration menu.

To set the TFTP server IP address via the phones menu, go to Settings and then Network Configuration. Go down to TFTP Address and press **# to bring up the hidden edit menu.

The main problem I had with this phone was it was password protected, but I didn’t know the password. I tried the default password of 1234 but that didn’t work, so I had to factory reset it. While in the settings menu press **2 on the phones key pad (not all together, but one at a time).

After saving the TFTP IP Address, the phone will reboot. If you watch the TFTP servers log, you should see the phone downloading the files.


It’s a nice 1 line, super easy phone. My biggest complaint is there is no speaker phone and SIP options are very limited. The phone does have keyhole openings in the back of the phone to make mounting on a wall real easy.

XBOX 360 Heatgun RROD Fix

I’ve been doing electronics for a long time and when a friend gave me a broke Xbox 360 with the RROD (Red Ring of Death), I jumped at the chance to try and fix it.

I googled the issue and found out it has to do with the use of Lead Free solder where the CPU/GPU/RAM/Bridge can develop broken connections. These chips are BGA chips, which mean they have the balls of solder under the chip itself so there is no way to visually inspect them. By searching, there seemed to be 2 ways to fix this, 1 was to replace the X-Clamps with screws and the other was to reflow the chips with a heat gun.

Replacing the X-Clamps

This way involves replacing the X-Clamp with bolts and washers so tight to warp the board/chip to make the connection. In no way do I recommend this to fix the RROD because by clamping the heatsink so tight, you can actually damage the chip. However, I do recommend replacing the X-Clamps with screws because trying to get these on and off can be a chore and one small slip with a screw driver, you can scratch a trace and damage the board. I used allen key (hex key) head screws, #10 x 32″ .

Heat Gun Reflow

DO NOT DO THIS! I will say this one more time, DO NOT DO THIS! We can, and do, learn a lot from the internet and I research things every day, but this is a bad popular myth. I do electronics all the time and design my own circuits, and this just does not make sense, but I figured why not try it anyway to see what happens. It failed, and failed bad. The traces bubbled and the chips fried even before I got the solder to melt. Lead free solder, on average, starts melting around 230C but a cheap heat gun runs at 300C (572F) on low (which is OK) and 600C (1112F) on high (which is just way too hot!). The bigger issue is applying that much heat to just the top of the chip will fry the chip. That big of a board really needs to have a preheater to heat the bottom of the board to around 170C and to just heat the chip itself to above 230C (until solder melts) from the top, so you’re only applying about 60C extra to just the top of chip. Also, you really need to monitor the board/chip temp with a thermocouple to make sure you’re at the right temp.


Pay someone to do a proper reflow or DIY it yourself with proper equipment. Make sure they use a thermocouple to monitor temps, a board preheater and a temperature controlled hot air reflow station. If I come across another RROD Xbox, I’ll try it on my reflow station.

Arduino Mega 2560

I picked up an Arduino Mega 2560 R3 clone on Ebay for $27.50 and it is definitely worth the money.  I was a little concerned that the construction might not be that great because of the price, but it has surprised me, construction is good and soldering is very professional (no cold solder joints that I can see).

My primary development machine is a Ubuntu 12.04 LTS box.  Installing the Arduino IDE was easy, I just followed Mark Loiseau’s instructions on his blog.  I have been playing with basic sketches and they compile and run great.

Overall, I am very happy with the product.

XBMC on Raspberry Pi

I have been playing around with the Raspberry Pi and XBMC a lot lately.  It has come a long was since it 1st came out.

I really like Openelec XBMC distro because it really does make the Raspberry Pi feel like an appliance since there is really almost no configuration necessary, it just works.  Most partitions are read-only, so if it crashes, you don’t have to worry.  But, that being said, it makes it a lot harder to tinker with.  I couldn’t get a GPIO remote to work and it was a pain to get other software installed on it.  It’s perfect if you have a USB remote sensor and you want to set it and forget it.

Raspbmc is another XBMC distro.  It is now on RC4 and its getting really good.  I like it a real lot.  Boot up times are not as good as Openelec, but since you boot it up once, then just let it go, it’s not a big deal.  It is based on Debian, so installing extra software is a breeze.  Also, since they have switched over to hardfp and other XBMC tweaks, it’s FAST!  Also, it comes with the lirc_rpi IR sensor kernel driver so getting a cheap ($1) remote sensor working was easy..

All in all, both distro’s are really coming along nice.  It’s impressive that the Raspberry Pi can do all that, or should I say it’s impressive with all the hard work that the developers did it get it to run on the Raspberry Pi.

Teensy USB Development Board

I started working with the Teensy USB Development Board from and I have to say it is nothing short of amazing.

The Teensy is an AVR microcontroller board and comes in 2 flavors, the Teensy 2.0 and the Teensy++ 2.0.  The Teensy has 25 I/O, 12 analog and 7 PWM whereas the Teensy++ has Teensy has 46 I/O, 8 analog and 9 PWM, but on both boards they have shared pins, so an I/O may also be an analog pin.

It’s almost like a Arduino, but smaller, runs full USB, and you can solder directly to it.  They both have their pros and makes a great addition to a makers toolbox.

Code is easy to create for the Teensy using the library’s or you can even put it in Arduino dev environment.

So for the $16, it’s worth a try.  Shipping was fast and the developer at PJRC seems like good person.

SDR with $20 USB Dongle

You can now have a SDR (Software Defined Radio) for $20!  The dongle is receive only, but it can handle from 64 MHz to 1700 MHz.  It works in both Windows and Linux.

The dongle is actually a USB DVB-T TV receiver that uses the RTL2832 chipset along with a E4000/FC0012/FC0013 tuner.  The DVB-T is not supported in the US, but there are plenty on eBay and elsewhere.  Here is a list of supported devices.

There is a pretty active group over at Reddit that has been helping each other out.

I have successfully run it under Linux with GNU Radio and in Windows with HDSDR using Balint256 drivers.

You can also follow our findings with SDR via the Wiki.

Wisdom Alarm Project

We have started a new project to interface to the Risco Group Rokonet Wisdom Alarm panel via the RS485 port.

Here is a link to the Wiki page of the project.

So far the code can read partition labels, zone labels, zone status, panel status, arm and disarm.  There are so many unknowns at this time, but we have a great starting point.

We do not have any protocol documentation, so if you can help get some, that would be very helpful and would speed the process along significantly.

We are looking for developers to contribute to this project and hopefully it can become a full Linux Open Source library.

Raspberry Pi

There is a new computer on the market called the Raspberry Pi.  I’ve been watching this project for quite some and am excited to see it finally being sold.  The Raspberry Pi was created by the not-for-profit Raspberry Pi Foundation in the UK.

The computer itself comes in 2 different versions, Model A for $25 and Model B for $35.  They are basically the same except Model B includes a NIC port and an extra USB port.


  • Broadcom BCM2835. This contains an ARM1176JZFS, with floating point, running at 700Mhz, and a Videocore 4 GPU
  • 256 Mb RAM
  • SD Card Slot
  • USB Port
  • HDMI Port
  • Composite TV Port
  • 3.5 mm Jack (audio)
  • No Power Supply

They have entered into a manufacturing and distributing contract with Premier Farnell and RS Components.  In the US, that means you can get them from Newark and Allied Electronics respectively.  Currently, the Raspberry Pi is being sold without a case, but that may change in the future.

The GPU has H.264 hardware acceleration built in which will allow you to watch high-def movies on it by just hooking up a TV with the HDMI port.

The whole computer is around the size of a business card and runs Linux!  This makes it perfect for our projects around here.


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