Resend again. Seems www.milkymist.org has been down 2 hours ago. :( On Mon, Mar 28, 2011 at 1:29 PM, Adam Wang <[email protected]> wrote:
> 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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