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This page records a few random notes about my system and what I had to do to get it working.


England - south coast

MythTV box

Lian-Li PC-C39B HTPC case
Asus M4A78-VM motherboard - onboard AMD RS780 (== Radeon HD3200) graphics processor 
AMD Athlon(tm) II X2 2.8 GHz processor
2048 MiB RAM
Samsung HD323HJ 320 GB SATA drive
TopSeed TSBX-2404 RF remote control

The Myth box runs as a standalone combined Frontend and Backend. It is a headless system (ie there is no mouse or keyboard attached) so system administration is done via VNC (using Remote Desktop Viewer) from another machine or by logging in over ssh.

Output device

The Myth box is connected directly to an analogue Sony Trinitron wide screen TV - the sort with a CRT tube! The TV is connected with a home-made cable which connects directly from the VGA output connector on the motherboard to the RGB SCART input socket on the TV.

The cable has a transistor gate built into it which combines horizontal and vertical sync from the motherboard (which has a Radeon graphics processor on it) into the combined sync signal needed by the TV. Although both X and xrandr seem to handle the 'composite sync' or 'CSync' flags correctly, I cannot get the Radeon processor to actually output composite sync at all, although the drivers and the device seem to support it. Hence the need for the sync combiner.

Also, the TV needs a voltage between 1V and 3V on pin 16 of the SCART connector to persuade it to switch to RGB mode. Examination of the input circuit of the TV reveals that it is tolerant to 5V, so the voltage was derived by simply connecting the VSync signal from the VGA connector directly to pin 16 on the SCART. VSync is high most of the time (assuming that it is set for negative sync pulses) and the brief negative going pulses are short enough to be ignored by the TV.

Software installation notes

Install MythBuntu 10.04 from CD
Enable ssh, nfs, vnc and mythtv services.
Don't enable samba.
Create first user as 'guest'. This user is automatically logged in and does nothing except watch TV.
No need to select a remote control or enable lirc as the TopSeed remote doesn't use lirc.
Remember to enable 'dvb firmware' drivers.