HiFive FE310-G002 JTAG on Board HiFive1 Rev B

HiFive1 Rev B
1

Hello,
I have 5 chips (FE310-G002) and I would like to build 5 PCBs with this chip.
Its for a university project to test RISC-V chips with JTAG.
I also have for testing and troubleshooting a HiFive1 Rev B board and a Sparkfun Red V board (very similar to the HIFive1).

Looking at both schematics (for HiFive1 and RedV) I see there is a USB-JTAG IC which works great and I can debug perfectly using openOCD.

But on my final board I want to use a third party tool (BusPirate) which is also a USB-JTAG and it is supported by OpenOCD.
My idea is to create a small board with the FE310-G002 , the Quad SPI memory, power regulators ICs and a lot of GPIO pins. I plan to leave the JTAG pins (we have FPGA programming experience so we have dealt with JTAG before) accesible so we can connect with the USB-JTAG interface.

So here is the question… I see that both the HIFive1 and RedV board have the JTAG pins accesible, but they are connected both to the FE310-G002 and the USB-JTAG IC.
I want to know if I can connect in parallel my own USB-JTAG and simply skip using the onboard USB-JTAG IC.
The idea is to test this BusPirate with OpenOCD before manufacturing the PCBs with the FE310-G002 on them.

Thanks,
Best Regards,
Edgardo

2

The HiFive1 RevB has a JTAG header between and inboard from the power LEDs and the Arduino power/reset headers.

Pretty sure it’s there to be used if you want to. Page 9 of the Getting Started doc says you can use it.

4.3 External JTAG probe header
The HiFive1 Rev B is populated with a 2x5, 0.05" pitch connector for use with an optional external
JTAG probe. This option would replace the on board Segger J-Link OB JTAG function with
an external JTAG debugger. This JTAG connector is compatible with the MIPI-10 0.05 inch
connector specification, as mentioned in the RISC-V debug specification.