On Mon, Jun 23, 2014 at 11:46 PM, Thomas Schmid <[email protected]>
wrote:
> Hello,
>
> We are trying to switch over our part programming to use CMSIS-DAP, since
> some of the newer parts we work with only support SWD programming. Our
> specific setup is the new Atmel ICE (EDBG version) with the Atmel SAMR21.
> We have it all working, but programming the flash is very slow (~1kB/s). To
> do some tests, I chose one of our other SAM4S platforms that can do both
> JTAG and SWD programming. Using a Segger JLink vs the Atmel ICE is like
> light and day (with same adapter_khz settings).
>
> Does anybody else have this problem, and maybe a solution for it? Or does
> anybody have an idea where the bottle neck could be? I started to look at
> the SWD signals, and there seems to be a lot of wait time between commands
> on the bus.
>
>
Hi!
The problem is that the CMSIS-DAP implementation in OpenOCD is synchronous,
i.e. it only has a single DAP access outstanding at any time. USB round
trips makes that unbearably slow. There are patches that are going to be
merged very soon that changes the API so that the driver can be rewritten
into an asynchronous style. But these patches are only to support the SWD
implementation for the FTDI driver, the CMSIS-DAP driver has not been
rewritten yet.
So your options right now are to:
1. Live with the slow speed and know that it's going to improve some time
in the future.
2. Get an ST-Link (like on the ST discovery boards) and live with the fact
that you won't have the same level of control (for example, no vector
catch).
3. Get a suitable FTDI based adapter and use the SWD patches currently in
Gerrit [1] (or wait for them to get merged). This option is speedy, i.e.
700 kByte/s memory R/W. Flash programming speed of course also depends on
the flash driver in OpenOCD and the actual flash controller.
4. Maybe the best option (for everyone else at least :)), rewrite the
CMSIS-DAP driver yourself, on top of the asynchronous API [2].
5. There's also the possibility to fix/update the JLink, Versaloon or RPi
SWD driver [3] that is also depending on the above API changes.
Also note that the EDBG CMSIS-DAP implementation is IMHO broken [4] and may
require quirks that harms performance, even in asynchronous mode.
Regards,
Andreas
[1] The change series ending with http://openocd.zylin.com/2184
[2] http://openocd.zylin.com/1959 which is also included in [1]
[3] http://openocd.zylin.com/2141 http://openocd.zylin.com/1947
http://openocd.zylin.com/2004
[4] http://openocd.zylin.com/#/c/2088/3/src/target/cortex_m.c,cm
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