How-To use the S-Video output of the APF9328DevFull. This way you can connect this board to a TV screen or a video projector.
For this functionnality, we use a Chrontel's CH7024 RGB to S-Video converter. This chip takes the signals coming from the i.MXL LCD controller and convert it to PAL or NTSC. This requires specific timings on these LCD signals and so you won't be able to see an image on both LCD and S-Video at the same time (i.MXL limitation).
Instead of using a Linux driver, a simple userspace tool (ch7024) has been written to configure the S-Video controller (through I2C bus).
It is now by default installed on a standard Armadeus rootfs. If not, you can add it in Buildroot configuration:
$ make menuconfig
Package Selection for the target ---> Armadeus specific tools/utilities ---> [*] ch7024 control
Once compiled you can copy the tool (buildroot/project_build_arm/armadeus/root/usr/bin/ch7024 + *.conf files) directly on you target in /usr/bin or reflash your rootfs.
Starting the tool
At first, the timings of the LCD controller have to be modified. This can be done by means of the imxregs tool. Do not forget to unlock the register access from U-Boot before.
320x240 input format (like MTFT035)
imxregs LPCR 0XF8C80087 imxregs HCR 0X78004401 imxregs VCR 0X0C001414 imxregs CSCR 0x03010003 imxregs SPCTL0 0x04011402 imxregs SPCTL1 0x00000040
480x272 input format (like LQ043)
imxregs LPCR 0XF8C80085 imxregs HCR 0x28000500 imxregs VCR 0x0c001617 imxregs CSCR 0x03010003 imxregs SPCTL0 0x04011402 imxregs SPCTL1 0x00000040
# cd /usr/bin # ch7024 configurationFileName.conf (ie: ch7024 ch424x283.conf)
Changing S-Video parameters
Changing the S-Video parameters is not easy due to several PLL parameters which have to be "fine tuned". An external tool (only running under Windows :( ) is required to do that. As the documentation for this component is restricted to registered Chrontel users ( no other choice :( ), please contact us if you need more informations.