Dave's RS232 - TTL - USB - serial interface thingy - Page 1
Forum section: electronics / beginners

author: andersthuresson
author_rank: Contributor
timestamp: March 02, 2021, 01:56:10 pm
content: Hi all! I didn't know where to ask this question so I do it here. I been watching older episodes of the EEVblog and EEVblog2. I came across an episode in EEVblog2 where Dave is trouble shooting a Siglent Signal Gen. That episode is dated 20/12-2017 in Youtube. In that episode Dave use a RS232 terminal program called Termite ver 3.3 and some kind of interface which seems to be RS232 / TTL / USB serial interface. It seems to be a useful thing to have in the tool box. Where to find that piece of hardware, or something similar that can be used to read serial data? I grabbed a picture of that nice little card that Dave is using.Cheers!

author: ledtester
author_rank: Super Contributor
timestamp: March 02, 2021, 03:47:13 pm
content: (btw, a link to the video would have helped a lot)There are a lot of cheap USB to TTL or RS-232 to TTL interface boards like these:https://www.aliexpress.com/item/4000120687489.htmlhttps://www.aliexpress.com/item/1005001587731393.htmlhttps://www.aliexpress.com/item/4000325072841.htmlJust search for "USB TTL" or "RS232 TTL".Some caveats:- TTL comes in 3.3 and 5V varieties so you'll want to get a converter board that is switchable between the two- Some USB UART chips have had driver troubles with different operating systems although I think that's been worked by now. To guarantee you won't have driver problem you can get one with a genuine FTDI chip (FT232) but expect to pay more. Note that almost every Arduino has one of the cheaper USB UART chips so I wouldn't worry about using them.

author: ledtester
author_rank: Super Contributor
timestamp: March 02, 2021, 03:59:25 pm
content: Just noticed that the Dave's board might also include isolation between the USB and TTL/RS232 sides.It's not something you will normally need, but in case you do you can look up "USB isolator" or "ADUM3160 module" on aliexpress/ebay for products such as:https://www.aliexpress.com/item/1005001658583980.htmlwhich should work at USB 2.0 low and full speed (1.5 and 12 Mbps).

author: andersthuresson
author_rank: Contributor
timestamp: March 02, 2021, 04:14:44 pm
content: Brilliant! These things are dirt cheap at AliExpress so I will order these things and start experimenting. Thanks for the input!

author: Monkeh
author_rank: Super Contributor
timestamp: March 02, 2021, 04:47:42 pm
content: There's a website printed right on the board..https://www.mario001.de/mikrocontroller/2014/08/09/usb-uart-interface/

author: tooki
author_rank: Super Contributor
timestamp: March 02, 2021, 06:57:10 pm
content: Quote from: andersthuresson on March 02, 2021, 04:14:44 pmJust beware that many of the ones that claim to be USB-RS-232 are in fact not RS-232, and instead use TTL signal levels (even if using a DB9 connector!!). So if you need actual RS-232 (for example, to interface with a piece of test equipment), look for there to be a MAX232 chip (or similar) on the board in addition to the USB-serial chip (FTDI, CHP340, etc).For UART-style TTL serial (like you'd use inside many devices), you don't need to worry about that.

author: Renate
author_rank: Super Contributor
timestamp: March 03, 2021, 11:43:39 am
content: Quote from: ledtester on March 02, 2021, 03:47:13 pmA genuine FTDI is guaranteed to have a unique USB serial string.Most $3 ebay things and fake FTDI's don't have this.For me, this is important, maybe not for you.In Windows a USB adapterwithouta unique serial number plugged into one USB port will show up as COM3, plugged into another port as COM5 (or whatever).Witha unique serial number it will always appear as a fixed COM number.With regedit you can change the "Friendly Name" to something intelligible.In Linux a USB adapterwitha unique serial number can be given a unique /dev/red_dvm (or whatever) from a udev rule independent of where/when it's plugged in.Code:SUBSYSTEM=="tty", ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6001", ATTRS{serial}=="A50429DJ", MODE="0660", GROUP="plugdev", SYMLINK+="red_dvm