Raw ADC data from CX23881 TV card
It is possible to use a TV card based on CX2388x chip to create a low cost high speed 8 bit ADC. During development, PixelView PlayTV Pro Ultra TV/FM card was used. Signal came from videocam and is applied at the video input of the TV card. Picture above is a rough representation of the captured data (generated from the captured data).
Sampling frequency is 27 Mhz. In Feb 2007, Jim Perkins tested other sampling rates by setting certain registers in the CX.
Driver and capture program source code can be downloaded below.
Programs are developed on Knoppix 3.4 Live CD running on 32 bit Intel/AMD single processor CPUs.
Try using e-Mule to get a copy of Knoppix 3.4 since www.knoppix.org no longer has this version.
WARNING 1 :These software are experimental software. Use at own risk. Driver crash may cause hard disk data corruption.
WARNING 2 :Modifying hardware voids warranty and can cause unrepairable damage. Do not try unless you are a qualified and knows what you are doing.
20 Aug 2005
Version 0.1 - 20 Aug 2005 cxdrv_v1.zip.
Captured data (using version 0.1 driver) from Pixelview PlayTV Pro Ultra TV card (all 8 bit unsigned)
sine wave (zip 2Mbyte) noisy sine wave, got DC offset ?
no signal (zip 1.5Mbyte) looks quite noisy and with DC offset ?
raw_tv.zip (zip 1.6 Mbyte) PAL composite video signal (Image above)
PAL composite video signal (zip 2.5Mbyte) Another capture
3 Nov 2005
Version 0.2. - 3 Nov 2005 cxdrv_v2.zip.
- Fixed bug in cxcap.c.
- Added support to tune TV/FM tuner.
- change ADC gain and offset.
1 Feb 2006 Update - Using Knoppix 3.7 Live CD
cxadc.c can also be compiled and used in Knoppix 3.7 Live CD. The following command will to the trick :
gcc -DMODULE -D__KERNEL__ -I/usr/src/linux/include -O2 -c cxadc.c
The rest of instructions are as in the included readme files. For Knoppix 3.7 Live, "uname -a" returns the following :
Linux Knoppix 2.4.27 #2 SMP Mo Aug 9 00:39:37 CEST 2004 i686 GNU/Linux
You need to a super-user to run mknod, insmod and rmmod. Run "su" to become a super-user. This is not mentioned in the readme files.
Knoppix 3.7 Live CD can be downloaded from www.kernel.org.
Knoppix 3.7 Live CD
Knoppix 3.7 Live CD MD5 hash
14 Mac 2006 Update - More recordings
A much better recording of sine waves (1 Mhz to 8 Mhz in steps of 1 MHz) was done by Jim Perkins using a modified driver of version 0.2. He also manage to get the CX2388x to sample at 20 MHz by writing 0xb2cb2e to the PLL Register at address 0x310168 and 0x2dd17 to Sample Rate Conversion Register at address 0x310170.
The recording was done on PixelView Play TV Pro Ultra which has a CX23883 chip. Signal is applied from DDS60 to video in. Extra components along the video in to the ADC input was removed with the exception of the DC blocking capacitor.