Where did the magic smoke go?

First project of the year - I2C Controllable RGB LED Nodes

2010-02-01T17:46:00.000-05:00

I actually started this project during the last week of 2009, and is one of the primary reasons I resumed blogging. Go figure, I haven't actually gotten around to posting it until now!

While I primarily focused on RF engineering in school, I have always had an interest in lighting, especially solid state lighting (LEDs). I have also always been in awe of those computer controlled animated Christmas light displays like that of Carson Williams back in 2005 or so.

More after the break...

I occasionally follow the development at Do It Yourself Christmas and have considered participating in development myself.

At the end of this year, I saw user mrpackethead's YouTube clip of his "Mega Tree" using 2000 individually addressable RGB nodes at . It is amazing, however, the nodes MPH is using are based on a controller chipset that is not available outside of Asia. As a result, I decided to start work on developing similar nodes using parts readily available in the USA. Eventually, I settled on the Atmel ATTiny25/45/85 AVR microcontroller due to previous AVR experience, and I2C for minimal pin count/pin use on the AVR. (Daisy-chain SPI was not achievable with an 8-pin AVR without sacrificing in-circuit serial programming.)

I prototyped my first node during Christmas break, and posted the results to DIYC in this thread.

At this point I have the following implemented:
24 bits/node (8 bits/color) control
Gamma curve applied to the input RGB, with internal 12-bit sigma-delta modulator for each color channel
Storage of I2C address in AVR EEPROM
A preliminary board design for the nodes I intend to send to Olimex next week

Source code for the project is located at my GitHub repository for this project.

Also, a video of a somewhat older version of my nodes is on YouTube at I2C-Addressable RGB LEDs - Breadboard Prototype

By the way, this project was the main driving reason for me purchasing the Rigol oscilloscope I discussed in previous posts. I also plan on posting more of my experiences with the Rigol and Linux soon.

Rigol DS1052E Oscilloscope and Linux - Part 2

2010-01-07T18:40:00.001-05:00

Well, after further investigation, I'm a dumbass.

The Python library I linked to in my previous post predates the usbtmc kernel module - it's libusb based!

So after "modprobe -r usbtmc" and running an example which sends *IDN? to the device, I get:


adodd@quadmonkey:~/Documents/ds1052e$ sudo ./usbtmc.py
[sudo] password for adodd:
Rigol Technologies,DS1052E,DS1ED113506705,00.02.02.02.00
adodd@quadmonkey:~/Documents/ds1052e$

IT WORKS! However, I'd like to try and find some documentation on the kernel module based approach, since it's likely more up to date.

Rigol DS1052E Oscilloscope and Linux - Part 1

2010-01-07T18:27:00.001-05:00

I just received a new piece of test equipment today, a Rigol DS1052E oscilloscope from Saelig. After powering it on and connecting one probe, I decided to see if I could interface with it in Linux. I've done some interfacing with test equipment in Linux before using USB-to-GPIB interfaces, but this instrument has serial and raw USB.

Trusty Google has yet to provide me any information about this combination, so I decided to start by plugging the scope into my Ubuntu machine. dmesg output and more after the break.


[65794.781221] usb 2-6.3: new full speed USB device using ohci_hcd and address 6
[65794.909328] usb 2-6.3: configuration #1 chosen from 1 choice
[65794.984233] usbtmc 2-6.3:1.0: can't read capabilities
[65794.984312] usbcore: registered new interface driver usbtmc

That error doesn't look promising, however it may be benign. Here's the lsusb output:


Bus 002 Device 006: ID 1ab1:0588  
Device Descriptor:
bLength                18
bDescriptorType         1
bcdUSB               1.10
bDeviceClass            0 (Defined at Interface level)
bDeviceSubClass         0 
bDeviceProtocol         0 
bMaxPacketSize0        64
idVendor           0x1ab1 
idProduct          0x0588 
bcdDevice            1.00
iManufacturer           1 Rigol Technologies
iProduct                2 DS1000 SERIES 
iSerial                 3 DS1K00005888
bNumConfigurations      1
Configuration Descriptor:
bLength                 9
bDescriptorType         2
wTotalLength           39
bNumInterfaces          1
bConfigurationValue     1
iConfiguration          0 
bmAttributes         0xc0
Self Powered
MaxPower                2mA
Interface Descriptor:
bLength                 9
bDescriptorType         4
bInterfaceNumber        0
bAlternateSetting       0
bNumEndpoints           3
bInterfaceClass       254 Application Specific Interface
bInterfaceSubClass      3 Test and Measurement
bInterfaceProtocol      1 TMC
iInterface              0 
Endpoint Descriptor:
bLength                 7
bDescriptorType         5
bEndpointAddress     0x01  EP 1 OUT
bmAttributes            2
Transfer Type            Bulk
Synch Type               None
Usage Type               Data
wMaxPacketSize     0x0040  1x 64 bytes
bInterval               0
Endpoint Descriptor:
bLength                 7
bDescriptorType         5
bEndpointAddress     0x82  EP 2 IN
bmAttributes            2
Transfer Type            Bulk
Synch Type               None
Usage Type               Data
wMaxPacketSize     0x0040  1x 64 bytes
bInterval               0
Endpoint Descriptor:
bLength                 7
bDescriptorType         5
bEndpointAddress     0x83  EP 3 IN
bmAttributes            3
Transfer Type            Interrupt
Synch Type               None
Usage Type               Data
wMaxPacketSize     0x0008  1x 8 bytes
bInterval               1
Device Status:     0x0001
Self Powered

There is very little information about this usbtmc driver available. There's a python library available from OpenMoko SVN.

I tried installing that, however it only gives an error when I try one of the examples. It may be related to that "can't get capabilities" error.

There is apparently an Agilent usbtmc driver in addition to the mainline Linux kernel one, I will try that later, as I need to go run errands now. Stay tuned!

A new beginning

2010-01-05T21:22:00.000-05:00

Once upon a time, a long time ago, I had a Livejournal account. I have not posted to that account, and while it still exists, it represented a very different phase of my life.

For that reason, I've moved to Blogspot and started fresh. Compared to my previous effort in blogging, this will have somewhat of a different focus. Rather than focus on personal issues, I plan on focusing more on various hobby projects.

More to come in the next few days... Over the holiday vacation I started a project that I need to start documenting, and I expect the oscilloscope arriving Thursday should lead to a few other small efforts.