Hi all, Am Samstag, den 26.05.2012, 15:32 +0200 schrieb Tomek CEDRO: > The main difference between LibSWD and Versaloon approach is that > LibSWD takes DAP operations and translates them to/from bitstream at > host level so it can be applied to any interface which makes it very > generic solution, while Versaloon takes DAP operations and transfers > them into interface that takes care of bitstream generation/analysis > which makes things faster over high latency links like USB but it > requires complex firmware for interface...
As a first note: I did nearly no code development on OpenOCD, but I'm quite familiar with JTAG (implemented some high-level command approach in real hardware for an ARM target) and I'm using OpenOCD in my all-day work quite happily. So, I somewhat disagree with the definition of a "generic" approach when talking about a bitstream. The bitstream is highly non-generic in my opinion. It's quite nice for "dumb" hardware, indeed. But as seen with the ST-Link, there may be adapters that simply don't support outputting bitstreams! Let's assume I'd want to support such high-level thing and the "generic" solution is to provide my driver with this generated bitstream. Now I would need to "parse" this bitstream again to form high-level "transactions" that I can send to my hardware. So, in my opinion there needs to be a layer in OpenOCD that is quite high-level (e.g. for JTAG: do a scan DR with 38 bits of data and go to idle afterwards), so that I can transform this "transaction" to the most optimal "format" or protocol that I can talk with my adapter. Here I could implement the transformation to a bitstream for "dumb" hardware. Maybe it would be good to have a layer here that does the transformation to a bitstream and couple another layer that "talks" the specific protocol my adapter uses. I have no real proposal (and even no time to implement something) of a new structure for OpenOCD, but the intention of my mail is to input another view of what "generic" should be in my opinion to support different kinds of hardware and not to focus too mich on the bitstream approach as "the solution" to all problems... Cheers, Manuel -- Manuel Borchers Web: http://www.matronix.de eMail: man...@matronix.de
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