Hi,
> (lesson learned: use lead for hand soldering of *QFP packages), we > managed to properly replace the two chips. > um..while running into this, lead hand soldering is preferred. > VIDEO INPUT > Replacement of the ADV7181 chip on my board restored the video input > functionality. This supports the theory that the chip was damaged > because of a voltage surge coming from my camera when it died. > Let's just add the Littelfuse transient voltage suppression devices on > the video input connectors of the RC3. > will add Littlefuse V9MLA0402 placed in the rear of each video input connector. http://www.littelfuse.com/products/Varistors/Multilater+Varistors+%28MLV%29/ML/V9MLA0402.html > AUDIO > After replacement of the codec, when playing the test tone with the test > program, the audio output was remarkably noise-free. > >From symptoms below you have had, i think that I don't need to sample WM codes. or you still want me to have some? as meanwhile you fine tune timing-related FPGA design bug that causes the AC97 link to become randomly corrupted, so I confirm with that later? > However, when running Flickernoise, the demo firmware, or the recording > tests of the test program, one or more of the following symptoms appear > (they are very marked with Flickernoise): > 1. "white" noise comparable to that of the LM4550 codec > ADC=> SNR A-weighted : 85dB(WM), 90dB(LM); typ. Frequency response: 19.2KHz(WM), 20KHz(LM); max. DAC=> SNR A-weighted : 95dB(WM), 89dB(LM); typ. Frequency response: 19.2KHz(WM), 20~21KHz(LM); max. Stop Band Rejection: 28.8KHz(WM), 70dB(LM) Out of Band Energy: -40dB(WM, LM) same resolutions: 18bits WM has more spec. ADC descriptions show up in datasheet then LM. Not sure which one is the key. > 2. very loud noises, beeps and screeches, sometimes periodic, happening > especially with Flickernoise and the demo firmware. They depend on the > activity of the software, e.g. moving windows, typing text, activating > certain functions affect the produced noises very significantly. > The link http://www.milkymist.org/IMG_0108.MOV shows: a Flickernoise 0.3 (built Mar 26 2011), Platform: SoC1.0 RC3, RC1 board Mine is Flikernoise 0.1 (built Nov 19 2010), SoC1.0 RC1, RC2 board which is LM4550B codec, it doesn't produce very loud noises like yours related moving windows, etc. > My guess is that there is some subtle and probably timing-related FPGA > design bug that causes the AC97 link to become randomly corrupted > depending on other SoC activity. This would give a simple explanation to > the audio problems we have seen so far: > 1. "white" noise on the ML401: same bug, same noise > 2. loud noises with WM9707: the two different codecs react differently > to the AC97 corruption (maybe because of slightly different timing > specs) > yes, even WM9707 is worse as above. > 3. audio input apparently not working in Flickernoise on Norman's board. > With the help of Murphy's law, process variations could have hit the > sweet spot that made the audio input pass the factory test and fail in > Flickernoise, because of different SoC activity with the test program > and Flickernoise. > so as a production side, I'd prefer to use test program rather than use Flikernoise, or we must to use Flickernoise to test M1? > Other (improbable) suspects could be: > 1. crosstalk, i.e. strong SDRAM signals aggressing the AC97 link. The > PCB layout has a good separation between the two, and increasing the > AC97 drive to 24mA on the FPGA does not change anything to the problems. > So this is unlikely. > yes, I don't think this could be the real cause since I was doubt that VGA RGB digital affects AC97 link, from last experiment(pulling low) this exactly eliminate my concerns on inner layer induced from rgb. It's quite a same routing that U14 Dram routes run inside layer with good ground seperately to AC97 links. > 2. strong power supply noise - we did not measure any > We didn't use a low ESR capacitor recommended on C235 output capacitor. I can replace tantalum one for a experiment about ripples on analog power. See www.avx.com/docs/techinfo/tantbench.pdf -Adam
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