Hi Am 27.08.2016 um 01:14 schrieb Nicolas Boullis: > Hi, > > On Fri, Aug 26, 2016 at 06:58:15AM +0200, Oleksij Rempel wrote: >> >> How about SPI? >> If yes, you can try this project: >> https://plus.google.com/102032716864870215256/posts/PwMMKYP5PKR >> https://plus.google.com/102032716864870215256/posts/QJqPxSi1Str >> >> Linux side is configured as watchdog, MCU side currently do only demo >> blinking, but watchdog should be a main future. > > Thanks for telling me about this project. > > But, to be honnest, I don’t really understand what this project is > about. I never hearded about the SSI32 protocol (while I know the SPI > protocol)… > > Anyway, as far as I know, my motherboard has no SPI bus… I guess I might > buy or design an USB-SPI interface, but I wonder if designing an USB > watchdog wouldn’t be easier… > > Anyway, I would still be interested to understand a little more what > that project is about; it might at least be a good source for > inspiration… > This project have different components levels: 1. SPI - it is cheap any mostly available on all SoCs and MCUs. IMO same can be implemented on UART. 2. Flow control line. SPI don't have it and if we use MCU with many tasks on other end, there is no way to predict where we can start our transfer. The are many ways to implement flow control on SPI, some of them implemented directly to IPcore which is not really portable. 3. Request/Interrupt line is muxed with Flow Control, it means by using 5 wire we still able to do slave to master transfer and flow control. 4. on transport level it has 4 byte header with some control information, size and checksumming. Practice has show that even on stable products we can get some weard DMA or FIFO related bugs so the transfer got corrupted. 4. LUN or Endpoint number, so one MCU can provide different functions at same time. For example watchdog, rtc clock, package filter, gpio extender. At same time since it all done in software we can use unified linux drivers. 5. App to App acknowledgement, so each side knows if package was actually delivered. 6. linux side bus implementation, so on linux we create a device tree with MCU capabilities and drivers are loaded automatically. In my link i provided a example watchdog driver, but in this case MCU is only toggling LEDs. Need more time to finish it. -- Regards, Oleksij
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