This is how to update the MACB firmware using the opensource tool xc3sprog


Setup (only has to be done first time)
--------------------
Install xc3sprog and fxload (ubuntu: sudo apt install xc3sprog fxload)

To configure the USB programmer:
Download xilinx.tar.gz and put the hex files in /usr/share

Download the udev rules and put it in /etc/udev/rules.d

Run:
sudo udevadm control --reload-rules

[Taken from https://github.com/timvideos/litex-buildenv/wiki/Xilinx-Platform-Cable-USB-under-Linux]

Plug in programmer and should work

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Programming a MACB

Open MACB side panel and connect JTAG programmer to port 

Plug MACB into NIM bin and power NIM bin on

Run
xc3sprog -c xpc -m -j

Expected output:
XC3SPROG (c) 2004-2011 xc3sprog project $Rev$ OS: Linux
Free software: If you contribute nothing, expect nothing!
Feedback on success/failure/enhancement requests:
        http://sourceforge.net/mail/?group_id=170565 
Check Sourceforge for updates:
        http://sourceforge.net/projects/xc3sprog/develop

JTAG loc.:   0  IDCODE: 0x16d8c093  Desc:                  XC2C128_TQ144 Rev: A  IR length:  8

This confirms the JTAG is working

Then to program  run

xc3sprog -c xpc -m . macb_apr20.jed

The directory should contain the macb_apr20.jed and the xc2c128.map files

Expected output:
XC3SPROG (c) 2004-2011 xc3sprog project $Rev$ OS: Linux
Free software: If you contribute nothing, expect nothing!
Feedback on success/failure/enhancement requests:
        http://sourceforge.net/mail/?group_id=170565 
Check Sourceforge for updates:
        http://sourceforge.net/projects/xc3sprog/develop

Programming row  81                                        
Verify: Success   

Now power off the NIM bin and remove the programmer and put the cover back on