Optically Isolated USB-UART adapter - Page 1
Forum section: electronics / general

author: Emil
author_rank: Regular Contributor
timestamp: December 02, 2017, 11:17:41 am
content: Hi,I launched a Kickstarter campaign yesterday for my optically isolated USB to UART adapter.https://www.kickstarter.com/projects/902741881/optically-isolated-usb-to-serial-adapter1.8V to 5V logic levels300 baud to 2Mbaud2500V isolationOverything except the board layout/gerber files are open source. I'm using Dave's version of the gear logo with letters:https://www.eevblog.com/forum/blog/eevblog-921-open-source-hardware-problems-solved!/

author: Emil
author_rank: Regular Contributor
timestamp: December 30, 2017, 11:05:04 am
content: Dave's latest mailbag shows my adapterEEVBlog #1049 - Mailbaghttps://youtu.be/eBzixNYF5K4

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 30, 2017, 11:16:35 am
content: Pity you didn't use the pretty-much-standard TTL232 header pinout for compatibility with existing devices

author: nctnico
author_rank: Super Contributor
timestamp: January 01, 2018, 01:41:16 pm
content: I'd like to see these kind of products in a standard casing instead of just another loose board. Please don't start with 3D printing because that isn't an off-the-shelve solution you can scale up to larger volumes easely.

author: Emil
author_rank: Regular Contributor
timestamp: January 01, 2018, 01:54:43 pm
content: Quote from: mikeselectricstuff on December 30, 2017, 11:16:35 amI didn't realize that there was a pinout that was common enough to be considered standard, so I just used a pinout I thought would be practical.

author: Emil
author_rank: Regular Contributor
timestamp: January 01, 2018, 02:22:16 pm
content: Quote from: nctnico on January 01, 2018, 01:41:16 pmJust to clarify, I'm not planning to sell 3D printed cases for the adapter, just provide files which people can print as is or modify to suit their needs.There is a few different reasons I didn't include a case: I think many people will use it without a case so the extra cost would be wasted for them. I don't know what kind of connector people prefer on the device side, so I would need to provide several with the extra logistics issued that implies, or go with one and possibly make something many people don't want. There is also the issue of longer time to market when getting enclosures with punched/milled holes for connectors, since it would take a round or two with prototypes from an enclosure manufacturer. I really didn't know if the adapter would be popular or flop completely, so the extra time and cost didn't seem worth it.Since there has been more interest than I was expecting, a future version with an enclosure is a possibility. I'm very interested in hearing from you and others what kind of form factor and device side connector you prefer.

author: nctnico
author_rank: Super Contributor
timestamp: January 01, 2018, 02:37:15 pm
content: This is one of my products which is similar to yours: a ruggedized USB to TTL serial converter (which can also serve as an NXP ARM microcontroller programmer and it has RS485 too). The case is standard but the front & rear panels are lasercut aluminium. I (reluctantly) designed it because there was nothing like it on the market and I didn't want to deliver boards wrapped in heat shrink tubing to my customers.

author: luftek
author_rank: Newbie
timestamp: January 01, 2018, 06:00:08 pm
content: Thank you for sharing!Maybe instead of CH340Gyou use CH340Cwhich does not need external crystal and is for some reason cheaper:https://lcsc.com/product-detail/USB_CH340C_C84681.htmlAccording to document:http://www.wch.cn/downfile/79C, B, E variants don't need external crystalI agree designing according to enclosure constraints should be one of priorities. Large shrink wrap won't do it.I recommend something like:https://www.aliexpress.com/item//32805387296.html3€/5pcs but probably something smaller would do

author: phil from seattle
author_rank: Super Contributor
timestamp: January 01, 2018, 06:19:37 pm
content: Quote from: luftek on January 01, 2018, 06:00:08 pmIs there an English translation of that document?

author: nctnico
author_rank: Super Contributor
timestamp: January 01, 2018, 06:21:20 pm
content: Quote from: luftek on January 01, 2018, 06:00:08 pmI wouldn't because it needs milling/drilling. An enclosure with panels you can replace with lasercut panels or PCB material is ideal for quick assembly.

author: luftek
author_rank: Newbie
timestamp: January 01, 2018, 07:18:51 pm
content: Depends on design. Yes PCB as front/rear panel is really handy. Have used it before.Better optical isolator ??:https://www.ebay.com/itm/USB-to-TTL-UART-RS232-Isolated-FT230-5V-3-3V-2-5V-1-8V/173023438576seems MAX12931 can do 1.8V out of the box?https://www.maximintegrated.com/en/products/MAX12931

author: voltsandjolts
author_rank: Unknown
timestamp: January 01, 2018, 07:24:00 pm
content: @nctnicoMay I ask, where did you source that case?

author: Emil
author_rank: Regular Contributor
timestamp: January 01, 2018, 08:25:44 pm
content: Quote from: luftek on January 01, 2018, 06:00:08 pmI have been using the CH340G for a few projects, but I wasn't aware of the CH340C, maybe because I haven't found a datasheet in English. Thank you for the suggestion.Looks like C and B should be drop in compatible on my board, but I would of course need to test that.Have you tried the CH340 parts without crystal? I think oscillator accuracy/stability is critical for USB, so if it's got an internal RC oscillator it would need to be a really good one(?)

author: Jeroen3
author_rank: Super Contributor
timestamp: January 01, 2018, 08:33:55 pm
content: Great board!I've made a dozen of those boards myself years ago as well. Using FT230X and Si8642, with the typical FTDI header.They have proven to beveryuseful and robust.I never bothered to commercialize them. Maybe I should as well...

author: Kjelt
author_rank: Super Contributor
timestamp: January 01, 2018, 08:40:50 pm
content: I use so many different usb adapters, like 3v3 ttl, 5v ttl, , rs485 and 232 so I bought an USB isolator to put in front. Only problem us the bandwith limitation, the stm8 serial link which is aprox 10MHz does nit work.

author: 0xdeadbeef
author_rank: Super Contributor
timestamp: January 01, 2018, 08:41:41 pm
content: Didsomething like this as wellsome time ago and found thePACTEC CNS-0407to be a fitting off-the-shelf case. I used an USB-B connector though.

author: Emil
author_rank: Regular Contributor
timestamp: January 01, 2018, 10:29:23 pm
content: Just a heads up. The Kickstarter campaign ends in 30 minutes.

author: Sjokolade
author_rank: Regular Contributor
timestamp: January 01, 2018, 11:23:59 pm
content: Can I choose between micro usb and type B connector ?

author: Emil
author_rank: Regular Contributor
timestamp: January 02, 2018, 06:28:21 pm
content: Quote from: Sjokolade on January 01, 2018, 11:23:59 pmYes, you can choose. There will be a survey before I ship the boards.

author: nctnico
author_rank: Super Contributor
timestamp: January 04, 2018, 06:07:39 pm
content: Quote from: voltsandjolts on January 01, 2018, 07:24:00 pmFrom Farnell / Element14:http://uk.farnell.com/multicomp/g403/enclosure-abs-grey-90x50x24mm/dp/1526727

author: Atika
author_rank: Contributor
timestamp: January 06, 2018, 10:57:22 pm
content: Quote from: luftek on January 01, 2018, 07:18:51 pmThank you for sharing our debug board on eBay store!! We inspired and launched our new version of debug board on kickstarter as well. Here is our test with 220VAC main: