f_ changed the topic of ##raspberrypi-internals to: The inner workings of the Raspberry Pi (Low level VPU/HW) -- for general queries please visit #raspberrypi -- open firmware: https://librerpi.github.io/ -- VC4 VPU Programmers Manual: https://github.com/hermanhermitage/videocoreiv/wiki -- chat logs: https://libera.irclog.whitequark.org/~h~raspberrypi-internals -- bridged to matrix and discord
<CarlFK> clever: im a little confused. I'm guessing I could add that header to my board, and then ... use a standard jtag programmer instead of the pi or pico host?
<clever> CarlFK: what i was thinking, is add a standard jtag header to the board, wired to the 40pin header, and make 2 of those boards
<clever> configure the host to bit-bang jtag, on the same pins as the target is using, so it goes thru the board just fine
<CarlFK> or if I have pi or pico host, plug in a 10 pin jtag cable that connects to 'anything' ?
<clever> then you can plug the 2 pi's together with a standard 10pin jtag cable, and the same pcb on both ends
<CarlFK> 40->10 (cable) 10->40 ?
<CarlFK> create a swis army knife of jtag options
<clever> yeah
<clever> and both the 40->10 and 10->40, are the identical board
<clever> as an example, connect gpio24 to the TDO pin on the 10pin header
<clever> for the target, 24 is in ALT4 mode, and acts as jtag
<clever> for the host, 24 is in gpio mode
<CarlFK> ah, I see what you are getting at...
<CarlFK> but I'm not sure how it makes things better
<clever> then you have the option of replacing either device with something else
<clever> you have a standard 10pin in the middle, and can replace the host with a standard usb jtag adapter
<clever> or replace the target with an fpga dev board
<clever> you also arent forcing the 2 rpi's to be in a specific layout, youll have a flexible wire between them
<CarlFK> I think I get the same extra features by adding the 10 to the 40-40
<clever> yeah, but then your board is also bigger
<CarlFK> yeah, but to me 2 boards and 1 cable is worse than one big board
<clever> oh, also, a lot of pcb fab houses, will give you multiple
<clever> so you have a minimum order size of 5 copies
<CarlFK> but 1 big board with the extra option of cables coming and going is appealing
<clever> so if your going to get duplicates anyways, design to use dups?
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<CarlFK> "There are no official standards for JTAG adapter physical connectors"
<CarlFK> What makes that 10 pin one special?
<clever> CarlFK: its just one i think ive seen in a lot of things
<CarlFK> got it.
<CarlFK> boards are so cheep, the connectors and cables will cost more than I save
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