Hi again, In the introduction of UBB, it says that it could allow Ben Nanonote to connect to other electronic devices, DIY things, Arduino, *SPI interfaces*. However, after a quick look at the datasheets of jz4720 and jz4755, I noted that besides to MMC/SD interfaces, the MSC_Dx in jz4720 could only be used as GPIOs. Meanwhile, the TF interface MSC1_Dx in jz4755 is multiplexed with SSI (including SPI), i.e. MSC1_D0 -> SSI_DR MSC1_D1 -> SSI_DT MSC1_CLK->SSI_CLK MSC1_CMD->SSI_CE0_ Does this mean that we have to simulate the SPI using GPIOs in Ben+UBB, meanwhile there is SPI controller available in jz4755? Thanks.
2011/4/9 Jianming Liu <[email protected]> > Hi David and Werner, > > Thanks for your suggestions. > > The current system is composed of a small SPI ADC board + 6410 EVB, with a > qt4 GUI in qt-extended4.4.3 environment. The ADC is connected to the SPI bus > of 6410 and I wrote a very simple and naive driver for > demostration, because I mainly focused on the GUI curve plot part before. > Therefore it is a good news that NN could support qt4.7, and it should work > for the GUI part. > > When it comes to the driver part, it is much more complicated for me, > because I do not have too much experience on this before. Luckily, the > system requirement is not very sensitive to high-speed and jitter, and > 5Ksamples/sec and even less would be quite enough. Meanwhile, we are more > interested in multi-channel implementation. Therefore, the UBB or SPI > controller will be both OK, and of course if we finally decide to design a > new board for this, we may use SPI bus for safety. But, currently, I am > wondering whether I could quickly write a very simple SPI ADC driver demo > based on UBB without considering too much about the jitter, rate, etc, and a > very low speed at user space will also be OK. Any hints or reference on this > will be welcome. > > Thanks. > > > 2011/4/9 Werner Almesberger <[email protected]> > >> Jianming Liu wrote: >> > I am writing to query about whether it is possible to use UBB to extend >> a >> > SPI ADC (ads8341), because currently I am designing a data collection >> system >> > using a SPI ADC ads8341 based on S3C6410. >> >> That should work, yes. One question is what sampling rate you need >> and how much delay and jitter your samples tolerate. UBB is >> bit-banged, so your maximum data rate is limited to something like >> 1 Mbps (or ~30 kSa/s), at 100% CPU utilization. >> >> The jitter depends on your trigger. Would you do periodic sampling, >> have a trigger signal, or would your program decide when it's time >> on its own ? For anything that uses a timer/external trigger, you >> need to consider the Ben's interrupt latency. >> >> Delay depends on latency plus how quickly you need to retrieve the >> sample. In the best case, if you have interrupt-driven operation, >> you'd first retrieve the previous sample and only then start the >> next acquisition and conversion. That way, you only need one >> interrupt per sample. >> >> > I am considering whether it is >> > possible use the UBB and JZ47xx instead for this. >> >> If "JZ47xx" means that you'll design your own board, then you could >> use the SPI controller and thus wouldn't have to worry about >> bit-banging. You'd still have to think about the other timing >> issues, though (like you would with any other processor). >> >> > How to implement the driver for this under Linux, >> >> That again depends on your requirements ;-) If they're modest >> enough, even a user-space implementation might do. >> >> Ben+UBB with a user-space driver may also be handy for prototyping. >> >> - Werner >> >> _______________________________________________ >> Qi Hardware Discussion List >> Mail to list (members only): [email protected] >> Subscribe or Unsubscribe: >> http://lists.en.qi-hardware.com/mailman/listinfo/discussion >> > >
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