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--- In Eddie Dawydiuk <> wrote: > > Hello, > > > We looked at the Marvell PDF documents from the TS-7800 page, and > > compared them to the source in ts7800ctl.c. We obviously are missing at > > least one key component to understanding because we weren't able to find > > anything in the sample source that seemed to match the documentation, > > except the string "TWSI" that appears in a few places. But, even it the > > source is accessing the Marvell, and we could figure out how to use set > > the timers to generate an interrupt that we could catch, it looks like > > the example functions for start/stop/read/write are WAY to 'sloppy' (in > > time) for use in setting a sub-millisecond timer, since they ignorantly > > use usleep(1) and usleep(100) all over the place when we all know that > > those may take as long as usleep(10000) (and any after the first almost > > certainly will take that long). > > The ts7800ctl code only touches the TWSI(aka I2C) registers in the > Marvell. Timing is not critical for the code that uses the usleeps as > the ADC samples are buffered in RAM(in the FPGA). I've recently reworked > the ADC code and written more verbose documentation on the ADCs. If your > interested you can find my work in progress here > ftp://ftp.embeddedarm.com/tmp/7800_adc_update/. I'm not sure this > updated code will help you access the timers in the Marvell chip, but I > believe the document will help you to understand what the ts7800ctl code > does with regard to interfacing with the Marvell chip(e.g. it only uses > the TWSI bus to send and receive commands to a microcontroller). Thanks, I'll grab your new ADC stuff and we'll take a look. And, FWIW, when I said "they ignorantly use usleep" I was referring to the lack of any comments indicating awareness that usleep() could take as long as 10,000 microseconds to return. As a long time maintenance programmer, that's the kind of code that makes one wonder how the hardware really works, and if the author understood the functions being used. In other words, a prime example of the source code providing very little trustworthy information, since it looks like it generally works by luck. And generally is a very deliberate choice of words, because, at least on our board, ts7800ctl doesn't work 100% of the time. Sometimes it gets (and doesn't handle, but that's expected in a demo, I guess) errors selecting, reading or writing. And a couple times it just kinda hung until we killedi it. Hopefully that helps explain why we're reluctant to attempt to learn anything from that particular source... __._,_.___
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