Any advice on a USB to RS232 connector

B

balanga

Any suggestions on what to look out for in buying a USB to RS232 connector?

I've just bricked a router and someone suggested I may be able to see what is going on if I can set up a serial connection.
 
One thing to check is if you need 3.3v or 5v. Usually it is the former.

You generally have 3 popular chips:
  • Prolific
  • FTDI
  • ch340
I use these:
The first one seems to contain a different chip every time I buy it. The second has a fantastic build quality (ch340) and allows me to specify 3.3v or 5v via a jumper. The third one is basically an Arduino that I misuse as a usb serial (ch340) at 5v.

They all tend to work quite well on BSD/Linux. I remember Prolific being annoying on Windows a few years back because they bricked cheap Asian clones by flashing their vendor id to 0. Since serial devices tend to be jumble-sale/bargain bin items, its sometimes difficult to actually get a genuine chip.

If you also have an arduino around, you can use that as a usb -> uart by bridging RST to GND. Genuine Arduinos tend to use FTDI, whereas the clones tend to use ch340.
 
I've used Silicon Labs CP2102 chip based adaptors to flash STM32 MCUs. CP2102 is 3.3V chip. Worked flawlessly on FreeBSD 10.4-12.2 and need no drivers on Win10.
I have troubles with CH340A on FreeBSD because I was unable to set 8E1 (even parity needed to flash STM32) on FreeBSD12.2. Don't know if it has been fixed. And it doesn't worked at all on FreeBSD10.4 (As I remember, one of the pins RXD or TXD does not actually receive/transmit anything, do not remember which one).
Didn't touch Prolific chips since 2007, but as I can remember they worked fine on FreeBSD 6-7
Never used FTDI chip based adaptors because they are more expensive.
 
shepper said:
There are a number of recovery methods depending on the Make/Model of your router. A good resource is the OpenWRT project:
General OpenWRT user guide

Specific OpenWRT Recovery Methods
Click to expand...
Actually it was in the process of trying to install OpenWrt on this router, a Teltonika RUT 955, that I bricked it.

The device reported that it was running OpenWrt and I did install the latest (Teltonika version) of OpenWrt via the GUI, then on the OpenWrt forum I found instructions for installing a newer, 'genuine' version of OpenWrt

OpenWrt firmware for Rut955 and with some 'help' from the good folks on the forum I managed to brick it!

Relevant OpenWrt thread
 
As kpedersen mentioned above, those chipsets work out of the box with FreeBSD. Personally I have dealt with FTDI and Prolfic.
E.g. this one is based on PL2303 (Prolific). "RS-232" should be in the title, not just "Serial" or "UART", and no TTL or 3.3V or 5V should be mentioned in the description. By the way, UGREEN in my link is a noteworthy brand, but there are many others.
 
aragats said:
As kpedersen mentioned above, those chipsets work out of the box with FreeBSD. Personally I have dealt with FTDI and Prolfic.
E.g. this one is based on PL2303 (Prolific). "RS-232" should be in the title, not just "Serial" or "UART", and no TTL or 3.3V or 5V should be mentioned in the description. By the way, UGREEN in my link is a noteworthy brand, but there are many others.
Click to expand...
Many thanks, I'll order one of these.
 
You must log in or register to reply here.
Back
Top