Anybody know why the JTAG on Arty A7.E0 does not work?

[concept]

Hello,

Does anyone have experience with the JTAG on the ARTY7 board?  i don't want to use the Digilent usb connector, instead i want to connect directly to J8.

1- Does the Diligent usb circuit need to be unsoldered so it does not drive the jtag pins on J8?

2- Does anyone know the manufacture PN for the connector (J8) that digilent designed in (with a zig zag footprint)?

Digilent doesn't want to show the connection from their usb jtag schematic, so its not clear if the jtag pins tri-state when the usb is not being used.  There have been other queries on this forum about this, and i have not found a clear and proper response to date.

So did anybody actually use J8 while the Digilent usb chip is installed on the board?

thanks

Matthew

[JColvin]

Hi @concept,

1. No, you do not have to unsolder it. There are tri-state buffers that disconnect the FTDI chip from the onboard JTAG nets when the FTDI chip is not open in Adept or Vivado; there are also some series resistors in place to protect circuitry from being damaged, though of course it is up to the end user to avoid deliberately creating drive conflicts. Figure 5 in the JTAG SMT3 Reference Manual shows the basic layout approach: https://digilent.com/reference/programmers/jtag-smt3/reference-manual#example_2interfacing_a_zynq-7000_while_retaining_the_xilinx_jtag_header.

2. You can use a standard straight 6-pin 100 mil header. The staggered layout is so that you can maintain electrical contact without having to solder an external header in.

3(ish). I personally don't often use J8, mostly because a lot of the designs I end up working with implement UART, and I already have a convenient connection to the host computer through J10 with the USB-JTAG circuitry.

Let me know if you have any questions.

Thanks,
JColvin