Usb <-> Rs485

[Kryten]

Hi
Is there anybody that has som schematics for a USB to RS485 converter??

 

[petrv]

No but I would take PIC18F2455 and MAX485, add crystal, connectors, a few capacitors and there you have an adapter. All that it will need is a firmware for the microcontroller ...

You can have a look at the Unicorn kit from blueroomelectronics

 

[Kryten]

Hmm sounds like a big box

Can it run on USB power?

 

[petrv]

if you use the SMD versions of the chips it won't be big. I don't see a problem running that on USB power.

 

[Kryten]

Cool Im looking in to it as we speak

 

[blueroomelectronics]

The FT232R has the schematic for a USB to RS485 converter in its datasheet.
**broken link removed**

 

[Kryten]

They dont provied samples

 

[petrv]

Hi Bill,

I don't know how I end up advertising your kits again ...

I was thinking about the FTDI chip as well but personally I prefer the PIC.
Both solutions have their advantages and disadvantages of course.

Petr

 

[blueroomelectronics]

Hey I always appreciate the plug I've used the FT232R and it's a nice chip. Would make an excellent USB to RS485 kit.

 

[arhi]

I used to use FTDI chips all the time .. and recently I decided to stop. I stopped when I found out that locally I can get FTDI chip for 8E and PIC18F4550 for under 7E .. so that simple truth removed FTDI chips from my order list. There is nothing FTDI can do that 18f4550 cannot (except, ok, ftdi is much smaller and use less power)

 

[blueroomelectronics]

FT232R
Pros no firmware or crystal needed, low power.

PIC18F2550 / 4550
Pros DIP package (if you don't want to solder a SOIC), and you get a nice microcontroller thrown in. I did find a FT232 emulator (firmware) on Xiaofan Chen's site.
Xiaofan's Blog: USB

 

[petrv]

I'd like to add that even if you do want to use SMD parts SOIC package (PIC18F2455/2550) is much easier to solder than FTDI chip in SSOP package, QFN is even more manual soldering unfriendly (I assume you don't have your own reflow owen ...)

 

[arhi]

@blueroomelectronics
I agree with pro's and con's but, how often do you make usb device without uC .. 90% of devices I made used FTDI in cooperation with uC on board. I usually do not pay attention on the cost, but when I noted that instead FTDI I can put 18f4550 I just stopped..

I'd like to add that even if you do want to use SMD parts SOIC package (PIC18F2455/2550) is much easier to solder than FTDI chip in SSOP package, QFN is even more manual soldering unfriendly (I assume you don't have your own reflow owen ...)

I never tried to manually solder FTDI what I do is I put solder on pcb, glue the FTDI on top of that (using flux as a glue, as it is sticky while hot) and then I put it in normal house oven for few minutes... never failed

 

[blueroomelectronics]

I'm not a fan of soldering SOIC and such myself, the best solution I've found is the Schmartboard system. Soldered a TQFP with it just fine.

 

[Ubergeek63]

I used to use FTDI chips all the time .. and recently I decided to stop. I stopped when I found out that locally I can get FTDI chip for 8E and PIC18F4550 for under 7E .. so that simple truth removed FTDI chips from my order list. There is nothing FTDI can do that 18f4550 cannot (except, ok, ftdi is much smaller and use less power)

Try writing to a thumb drive with a 4550...

 

[blueroomelectronics]

Try writing to a thumb drive with a 4550...

Can't do it with an FT232 either.

 

[Ubergeek63]

I'm not a fan of soldering SOIC and such myself, the best solution I've found is the Schmartboard system. Soldered a TQFP with it just fine.

What size? I did a 100 pin 0.5mm pitch by hand...not fun. Worse still was modding a board by lifting and soldering to two adjacent pins on that thing!

 

[blueroomelectronics]

0.5mm, easy with the Schmartboard.

 

[Ubergeek63]

0.5mm, easy with the Schmartboard.

Actually I was soldering to a custom PCB I had designed. I have never heard of Schmartboard, curious that it is actually reasonably priced. I do not, off hand, see the difference between the "old" and the "EZ".

 

[Kryten]

Bill where on Xiaofans site did you see the emulator.

Im really going to make it for a buddy, cous the factosy made stuff are really expensive (beeing a student and all)