19:49 <sys64738> hi, im working on some code that turns the rpi pico into an ft2232 clone (without knowing much about the low level details about jtag), and, is it ok to pause the clock signal in the middle of transferring a command, or does the entire command have to be sent in order for things to work? (usb has a max packet size of much less than the 65536 supported by the mpsse protocol, so, these would have to

19:49 <sys64738> be split up, and keeping the timing consistent between multiple usb packets sounds like itll be annoying)

19:50 <sys64738> (asking here because #openjtag doesnt seem to exist yet? and ##openjtag is practically empty)

20:14 <PaulFertser> sys64738: hi

20:16 <PaulFertser> sys64738: I can't answer your question (I can't outright remember any reason for it to be not ok) but I'm interested why you decided to implement MPSSE and not cmsis-dap or jlink protocol.

20:17 <sys64738> i have to admit that the decision wasnt very informed

20:17 <PaulFertser> As MPSSE was meant to be implemented in ASIC right from the beginning, and the other protocols are implemented by MCUs.

20:19 <PaulFertser> sys64738: btw, have you checked openocd src/jtag/target/mpsse.c? It reads out the maximum packet size from the USB descriptor so you should be able to specify it as your hardware permits.

20:20 <PaulFertser> descriptor->endpoint[i].wMaxPacketSize;

20:20 <sys64738> i mean it was mostly "ok it seems to have been done before (eg. https://github.com/Disasm/f042-ftdi/), it doesnt have to do 'smart' stuff but its just pushing bits, and also flashrom has an ftdi driver as well so thatd also come for free"

20:20 <PaulFertser> flashrom has jlink driver too

20:20 <sys64738> ah i see, thanks. now lets hope libftdi does that too, for flashrom

20:22 <sys64738> also with the pio in the pico/rp2040, i dont think itll be much of an issue to turn it into nicely clocked signals, its mostly the delay that was bothering me. but i guess if openocd limits it itself, it isnt that much of an issue then

21:01 <sys64738> hm i just discovered that https://github.com/raspberrypi/picoprobe/issues/2 is a thing already

21:05 <PaulFertser> Nice link

21:10 <sys64738> ok so theres a version taht runs code on one core of the rp2040 to debug the other core; and theres a version to use swd to debug other hardware. but only swd and no jtag, and i dont think my ecp5 has swd support?

21:12 <sys64738> sooo still not that useful for my case :/

21:20 <PaulFertser> sys64738: cmsis-dap protocol has jtag too

21:20 <sys64738> yes but the pico implementation doesnt

21:21 <PaulFertser> But you can extend it with code from daplink.

21:21 <sys64738> https://github.com/majbthrd/DapperMime/blob/master/bsp/rp2040/DAP_config.h#L84

21:22 <sys64738> though it doesnt seem that difficult to extend

21:22 <sys64738> ( https://github.com/majbthrd/DapperMime/blob/master/bsp/rp2040/DAP_config.h#L332 + following lines)