Looks like the issue may be with macOS.
I tried in Mojave with minicom and screen, and I got the Linux login prompt after a hitting enter a few times. Strangely, every time I hit enter, odd serial characters came up until about the 5th or 6th time, then I got the normal login prompt. On the HDMI-connected monitor, I saw a SysRq prompt come up. It seems like hitting enter must have hit the magic key combo for the linux sysrq prompt.
So, I loaded up Kali in a VM and passed the USB device (FT232 with RXD/TXD/GND connected) and ran minicom (turned off HW flow and turned on SW flow) and was able to see everything including the SPI boot messages.
Let me know how it goes for you.
-Yama
I tried in Mojave with minicom and screen, and I got the Linux login prompt after a hitting enter a few times. Strangely, every time I hit enter, odd serial characters came up until about the 5th or 6th time, then I got the normal login prompt. On the HDMI-connected monitor, I saw a SysRq prompt come up. It seems like hitting enter must have hit the magic key combo for the linux sysrq prompt.
So, I loaded up Kali in a VM and passed the USB device (FT232 with RXD/TXD/GND connected) and ran minicom (turned off HW flow and turned on SW flow) and was able to see everything including the SPI boot messages.
Let me know how it goes for you.
-Yama