usb-ttl converters question

Hi, Ive been looking around everywhere, and have had no luck so far finding the answer to ths question:

I see some people say that they use the FT232 chips, others use ATTiny chips, cp210 chips, or MCP chips from microchip to do the usb-ttl conversion. Ive also seen people talk about mid print disconnects while using the FT232 chips, and my question is this:

Are the disconnection issues only related to FT232 chips, or are they common among all usb-ttl chips? I ask because Im currently working on a usb-ttl converter board and I have a bunch of pl2303x chips, and wondering if I will experience the same issues with that chip as the FT232? I know the FT232 has latency issues, which leads to the disconnects, but Im curious if it was only the FT232 chips that had that issue or if if I'd find the same problem in the pl2303 chips also?

Also I plan on running my printer connection at 115.2k, and wondering what the chance of getting the issue if I did use the FT232 chips?

Edited 2 time(s). Last edit at 09/19/2013 01:15AM by cae2100.

Does anyone know? Main question I just want to know is what is the chances of the thing crapping out mid print if I do use ft232 while running at 115200?

First off, afaik, its usb to serial. The *TTL* designation means transistor-to-transistor-logic, which is different altogether and refers more to hardware gates and related.

Also most of reprap electronics use FT232RL and works ok, i also have one and also works ok on a vanilla mendel. I think the change away from FT232 occurred only with use of arduino mega which started to use an programmed atmel chip instead of ft232, but except that, probably the most used reprap usb to serial converter is still ft232.

If you have any doubts, buy a module UM232R, thats a complete solution for usb-serial conversion with ft232rl and all support components.

I understand how that all works, Ive used the stuff with microcontrollers for around 2 1/2 years now, but was just curious how it affects the 3d printers in the aspect of different usb chipsets compared to others. Also the chance of the connection cutting out. like How many times have you run into the disconnect issue on your vanilla mendel, how often does it occure, and what speed do you run your connection at to avoid the issue of it cutting out mid print?

Ty for your reply also

I have had disconnects with native USB and non-FTDI chipsets, so I don't think it is a particular feature of FTDI. It is more to do with the design of USB, and partly the implementation, i.e. good grounding and shielding.

The baud rate I think is irrelevant to USB, since the USB always runs at USB speed. The baud rate may affect the ability of the firmware to keep up with the data though.

> I know the FT232 has latency issues, which leads to the disconnects

I hadn't heard that, and I can't think why latency leads to disconnects. Do you have any more info on that?

IME, disconnects are caused by electrical noise on the USB data lines.

Ive seen alot of things about the latency with the ft232 chips, and causing issues with the microcontrollers. If you look around google, you'll see a bunch of people with that issue, and Ive experienced it a time or two with the ft232 chip that I had when using it with the PIC microcontrollers.

Also, thanks a ton for the answer, that gave me pretty much all of the info I was needing. I may just use the pl2303 adapters that I have a ton of. (thanks ebay and extremely low prices, and accidently putting 10 in the amount box )

Also, I think eventually, I may just use it to start the printer working, then later run the serial port connector through a level bss138 based level converter, and hook it up to the serial port on the raspberry pi, which I was planning on building into the printer anyhow.

Thanks again for the info.

Oh well, if you want to investigate things, or actually want to get something to fail it or disconnect it on purpose, take a tool like this angle grinder, put it on a socket with same phase and neutral with the printer. Start comms, and then power up the angle grinder, and i give it a very good chance your comms will fail when that happens, due to reactive current issues. On a large scale if you are located right near the mid voltage to low votage trafo box, or if your phases have capacitors or reactors for reactive power, then comms have a chance, but these things are more for industrial areas. Or, on a low scale what it can be done, if the used psu has overkill capacitors or active cos phi improvement/control (hi-end atxs), then comms again have a chance to survive, but i think chances to survive without any of that are low. If it doesnt fail with the angle grinder, then time to try an old style metal arc-welder - thats probably better at killing comms - almost a guarantee. Let us know how that worked And have fun, lol

Just stuff like this have little to do with the ics themselves. The ft232rl is probably an old one by now, and as such probably it could be said its in the reliable part of its lifecycle. For this conversion probably all ics solutions are rather old by now, so i wouldnt expect much differences from one to another.

ok, thanks, but I wont really have anything that would cause that much noise around it tho, and I have a power supply with a bunch of massive caps in it already, designed for gaming systems, and for noisy environments like shops and such. I got it bc I figured with all of the spikes and noise from the 5 motors running all at once, it would be better to go for something like that. Also, the most electrically noisy thing that I have is my laptop psu, (cheap ebay one) and when I plug it in, it sends static and everything else through the TVs and messes up all radios and monitors around it, and I had it plugged into the same port as the printer, and there was no issue with comms at all.

I had a little trouble with stuff at first on my 1.4.1 gen7 board, with the brownout detection, but realized that they made a goof on the site, and said 100uH, but it really needs a 10uH or it will cause that. After I fixed that, I havnt had any issues, but I just wanted to be sure that it didnt cut out half way through a print and mess up because of the fact that this printer will be taken around and such to different places like family member's homes and such, and hate to try showing off how it works, and the printer just shut down mid print and mess up making me look like a fool.

Thank you again and I'll check out the angle grinder if I can find someone with one, or find one.