Serial Console on Zyxel NSA 320 , needed before flashing uBoot (1 reply)

I have a functional Zyxel NSA320 that I would like to replace the older drives and install Debian and new u-boot etc. The NSA320 is currently set up as JBOD. Currently everything is original with a few addons for NFS etc. With Debian I only need NFS and SMB for file storage, with sleep wol etc.

I have read many of the instructions but stuck at the very beginning "Flashing uBoot to mtd0 could potentially brick your box! please have serial console, or JTAG set up before hand to recover from any mistake or bad flash"



My computer is running Ubuntu-Mate Release 22.04.3 LTS, Kernel Linux 5.15.0-91-generic x86_64

Using a Dtech USB to UART TTL Cable that supports 3.3 and 5v VCC , and

dmesg | grep tty

pl2303 converter now attached to ttyUSB0

minicom -D /dev/ttyUSB0

connects 115200 8N1 ttyUSB0


NSA320 Pins:

+----+----+
| | |
+----+----+----+----+----+
|3.3V| TX | RX | | GND|
+----+----+----+ +----+

Dtech manual :

TXD = White
RXD = Green
GND = Black
VCC = Red


Note: I did not connect the VCC line because the Mudslide website stated the VCC was not needed, but did the TX-white RX-green GND - black


When I turn on the NSA320 all I get is a little grey diamond shape with maybe a question mark, not sure, it is pretty small, no other output.


I tried shorting the TX and RX on the cable and I can see everything I type.


What am I missing/doing wrong?

If I read it correctly I should see boot up information, but all I get is 1 tiny Diamond shape.


The NSA320 is working as it has for many years, with or with the cable connected.



Thank you in advance,


joe