Not really an issue, but wanted to share this setup. I was able to get HSU working on a raspberry pi 4 and elechouse chip. It is a lot faster than I2C and uses the same number of wires.
The hardware switches on the chip board need to be set to "00".
Plug the NFC device into 3.3v power, SCL to TXD and SDA to RXD.
Run "sudo raspi-config" go to interfacing options -> serial.
Select No for terminal output, and Yes to expose hardware. Reboot.
Not really an issue, but wanted to share this setup. I was able to get HSU working on a raspberry pi 4 and elechouse chip. It is a lot faster than I2C and uses the same number of wires.