Re: [Discuss-gnuradio] VGA-based DVB-T modulator
Probably Tempest for Eliza: http://www.erikyyy.de/tempest/ There's yet another similar project that I would like to track down that was using a VGA card. I wrote a fm transmitter using the vga output and called it Tempest for MP3 FM. I packages it together with the am transmitter from tempest_for_mp3 and put it in tempest_for_eliza-1.0.6.tar.gz You can find it at: http://www.olifantasia.com/pub/projects/am_crt/ http://www.olifantasia.com/pub/projects/am_crt/tempest_for_eliza-1.0.6.tar.gz greetings, Martin ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] VGA-based DVB-T modulator
Does anyone here know if the VGA cards prevent you from controlling the DAC durinng the blanking intervals? Are the blanking intervals implemented in hardware or in software? Generally, video cards stop squirting bits during the blanking intervals, which are implemented in software. This lets the adjacent rows of the frame buffer be next to each other in the memory that the video hardware is scanning its way through. However, the timing of the blanking intervals can be controlled with a fair bit of detail. These are those terrible X config modeline values that can blow up your monitor if you set them wrongly. There will be *some* blanking interval, but it can perhaps be very short and can perhaps occur at an interval that won't often affect your signal. It would be great if video hardware had a mode that turned off this foolishness and just kept scanning out a section of RAM, raw. This would even improve refresh rates on things like LCDs that don't have to move an electron beam back across the screen during the horizontal retrace time. But few video chips probably do. John ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] VGA-based DVB-T modulator
On Tue, Jun 14, 2005 at 02:36:48AM -0700, John Gilmore wrote: Does anyone here know if the VGA cards prevent you from controlling the DAC durinng the blanking intervals? Are the blanking intervals implemented in hardware or in software? IIRC correctly, on some of the high end video cards (e.g., nVidia) it's all controlled by microcode running on the custom chips on the boards. On those cards I think that with suitable inside information you can control everything. Eric ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] VGA-based DVB-T modulator
Someone proposed this a while ago, but Fabrice Bellard (who is also responsible for cool stuff like the tcc compiler, which lets you use C as a scripting language and lets the Linux kernel compile itself at boot time) has used a VGA card's DAC as an RF modulator to produce a valid DVB-T signal. He uses a static greyscale image displayed under X11 with weird video timings, and connects two of the VGA pins to a coax cable. It generates a DVB-T signal on DVB-T channel 5 in VHF (around 176 MHz). He has also produced PAL and SECAM VHF equivalents by the same technique. http://fabrice.bellard.free.fr/dvbt/ (via slashdot) So it looks like you can use a VGA card as a source of arbitrary VHF waveforms (at least arbitrary periodic VHF waveforms) without an upconverter. Bellard seems to think that you could use it to do nonperiodic waveforms too. -- Seth David Schoen [EMAIL PROTECTED] | Very frankly, I am opposed to people http://www.loyalty.org/~schoen/ | being programmed by others. http://vitanuova.loyalty.org/ | -- Fred Rogers (1928-2003), |464 U.S. 417, 445 (1984) ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] VGA-based DVB-T modulator
Seth David Schoen wrote: Someone proposed this a while ago, but Fabrice Bellard (who is also responsible for cool stuff like the tcc compiler, which lets you use C as a scripting language and lets the Linux kernel compile itself at boot time) has used a VGA card's DAC as an RF modulator to produce a valid DVB-T signal. I sure wish I could remember where to find it, but I've seen demonstrated a program that would generate valid AM waveforms by displaying certain pictures on a video screen. You'd enter a target frequency (I think in the HF range) and choose a MIDI sound file, and it would modulate the CRT display to emit RFI at that frequency with the tones riding as AM modulation. Very spooky. It was a demonstration of the security hazards associated with CRT displays (TEMPEST stuff) in a very palpable way. -Johnathan ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] VGA-based DVB-T modulator
On Tue, 14 Jun 2005 08:17, Johnathan Corgan wrote: I sure wish I could remember where to find it, but I've seen demonstrated a program that would generate valid AM waveforms by displaying certain pictures on a video screen. You'd enter a target frequency (I think in the HF range) and choose a MIDI sound file, and it would modulate the CRT display to emit RFI at that frequency with the tones riding as AM modulation. Very spooky. It was a demonstration of the security hazards associated with CRT displays (TEMPEST stuff) in a very palpable way. There's a link on the page Seth sent.. http://www.erikyyy.de/tempest/ -- Daniel O'Connor software and network engineer for Genesis Software - http://www.gsoft.com.au The nice thing about standards is that there are so many of them to choose from. -- Andrew Tanenbaum GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C pgpaatl1T6Tto.pgp Description: PGP signature ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] VGA-based DVB-T modulator
On Tue, 14 Jun 2005 09:15, Seth David Schoen wrote: There's yet another similar project that I would like to track down that was using a VGA card. Does anyone here know if the VGA cards prevent you from controlling the DAC durinng the blanking intervals? Are the blanking intervals implemented in hardware or in software? I believe you define certain parameters (including the blanking interval) and the video card only reads data for 'valid' parts although I don't think there is anything that would stop you making a modeline that was very small, or maybe even non existant. -- Daniel O'Connor software and network engineer for Genesis Software - http://www.gsoft.com.au The nice thing about standards is that there are so many of them to choose from. -- Andrew Tanenbaum GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C pgp6WxK3Umcck.pgp Description: PGP signature ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
