Troubleshooting

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No image and no sound

Insure the composite audio/video outputs to your TV are not inversed.

No image and High pitch noise

  • There's nothing in the screen or bunch of random lines/dots appears
  • The sound is a horrible high pitched noise out the speaker


Insure *only* these fuses are written (this means checked in AVRStudio) (written fuse=0, unwritten fuse=1):

IF you are using a crystal:

-SPIEN (pre-written in the factory)
-EESAVE
-CKSEL3
-SUT1
-These fuses correspond to a setting of 0xD7 for lfuse and 0xD7 for hfuse

IF you are using an oscillator module:

-SPIEN (pre-written in the factory)
-EESAVE
-CKSEL0
-CKSEL1
-CKSEL2
-CKSEL3
-SUT0
-SUT1
-These fuses correspond to a setting of 0xC0 for lfuse and 0xD7 for hfuse

EESAVE preserves the eeprom between flash writes (will be useful later on). CKSEL=0111 SUT=01 starts with a full swing oscillator 16K delay+0ms.

Mega644s ships with CKDIV8 AND JTAGEN activated and must be uncheked. CKDIV8 internally divides the master clock by 8, so your Uzebox runs at 3.57Mhz. No chance it will generate video with that! Also JTAGEN activates the debug port, which is on the VIDEO DAC port and will screw up some color component if left active.

Colors are weird or missing (i.e. green)

Insure the JTAG fuse is not programmed since it activates the debug interface on some pins of PORTC.

The video signal on the S-video output exhibits a "checker board" pattern.

This is most probably a ground problem. Ensure the S-video connector's metal casing is soldered to your ground plane.

Weird graphics glitches or random crashes when using different optimization level

Insure you *always* clear r1 before calling C routines from assembler functions otherwise, results can be unpredictable.