16:54 <tim42> Hi. I was reading about OpenOCD and through the docs for the first time this week. It seems like every USB adapter speaks its own bespoke protocol? Or at least there's a ton a different families. Is there a preferred or standard one within OpenOCD that new adapters should implement instead of making up a new one?

16:56 <PaulFertser> tim42: hi

16:56 <PaulFertser> tim42: probably CMSIS-DAP

17:00 <tim42> PaulFertser: thanks. I'll read up on that one.

17:01 <PaulFertser> tim42: are you building a new adapter? For what purposes and based on what hardware?

17:22 <tim42> Well, not really, but maybe. I was poking at a cloud based IoT device I have and trying to get some local control of it. I saw an article where some security researchers had dumped the firmware using its JTAG pins, and thought I might give that a try, and started reading about different adapters. Then I started wondering if I could make one out of

17:22 <tim42> what I had on hand already, and found a couple of projects. The last one i looked at was "pico-dirtyJtag", and saw it needed a patched version of OpenOCD.

17:24 <tim42> I clicked through to the gerrit PR and was reading some of the discussion, and it sounded like even the author didn't fully understand the protocol it uses to talk to OpenOCD, and between that and reading the OpenOCD manual and seeing all the different devices, I started asking myself "why is it like this?"

17:28 <PaulFertser> I see

17:29 <PaulFertser> One of the most popular is MPSSE protocol by FTDI, they just implemented it in hardware in their ICs the way they wanted. Another is J-Link which they implemented in software for their products. CMSIS-DAP is an attempt by Arm to make another standard.

17:42 <tim42> Are some of those better than others? I got the impression some adapters talk at a higher level and offload more to the adapter, and some I guess put the "adapter" in adapter and OpenOCD is toggling pins over USB, which I've read adds a lot of latency.

18:26 <PaulFertser> tim42: all modern debug protocols designed to be used over JTAG or SWD transports are designed in a way to provide very good bandwidth despite the link latency. It's not just bitbanging over USB, no, the queue can get very long and submitted in a single message.

18:26 <PaulFertser> So all popular adapters provide means to do that.

20:42 <Hammdist> hi all. I'm trying to flash a colorlight v8 using openocd from linux. I have an ft232h breakout board. so far I have connected GND to GND but I'm not sure if I should connect the breakout board's 3.3v pin to the colorlight's 3.3v pin. I will want to power up the board and program it while it's powered. is it correct to only connect the grounds?

20:46 <PaulFertser> Hammdist: hi

20:46 <PaulFertser> Hammdist: is it just ft232h breakout, no extra components?

20:46 <PaulFertser> Hammdist: do you have schematics for it? How is Vccio pin connected?

20:48 <Hammdist> I will look for the schematic. here is the product page meanwhile: https://www.adafruit.com/product/2264

20:48 <Hammdist> schematic located: https://learn.adafruit.com/adafruit-ft232h-breakout/downloads

20:49 <PaulFertser> Hammdist: don't connect 3.3 V with that

20:50 <Hammdist> so it should work if I just connect the grounds and power the board though it's power plugs?

20:51 <PaulFertser> Hammdist: I would expect it to.

20:51 <PaulFertser> Hammdist: sometimes for proper communication series resistors are needed, sometimes not, you'll see.

20:52 <Hammdist> my next question is how do I know the default pinout for ft232h from openocd? on the breakout board I have ports D[7:0] and C[9:0] ... how to the jtag signals map to that?

20:52 <PaulFertser> Hammdist: you need to take a look at MPSSE signal table

20:55 <PaulFertser> Hammdist: actually, it's also documented in interface/ftdi/ft232h-module-swd.cfg

20:56 <PaulFertser> (JTAG signals all have hardware fixed location, there's no non-default layout)

20:57 <Hammdist> ah thanks. I was finding pin assignment for all other chips except ft232h

20:59 <PaulFertser> Hammdist: you do not need TRST or SRST for SVF playback.