USB to RS232

Well you have thrown a wrench into my plans.....

But after looking at things a FPGA would be a nice solution that we could use in other applications (RS485 for example)

Im looking at the Lattice XP2.

In the end the circuit will look a little like this.

Sure simplifies what I had already started using the conventional method. This will reduce the cost and IC count for sure.

I`m going to buy the proto board to get things moving. In the background I`ll create the PCB and maybe intigrate the CPU.

Looks like you're making some progress Tom - am I right in thinking you wanted separate grounds though for the serial ports?

If you want isolated ports, I've used onto-isolators in the past for the Tx and Rx signals, and a dc-dc convertor to isolate the power supplies for each channels MAX232 chip. You need to be wary of the speed of signals through the opto-isolators (limited myself to 2400baud once.... don't want anyone to repeat that mistake! ).

TI have done a reference design using a capacitive isolator, and powered that from the RS232 line itself, which might be an interesting read and something to consider - http://www.ti.com/lit/ug/tidu298/tidu298.pdf

A

I think I have one of those dev boards - although with Lattice I usually go straight to a custom pcb because I know the parts quite well.

You'll need a clock and a debugging port (can be used to program it on board as well)  for the FPGA in the final design.

MK

abrain

Yes I need separate grounds for sure.

• Did you mean opto-isolators?
• I will look at that link for sure

michaelkellett

• My thoughts exactly!!  I have started the board layout already
• If you guys like I will post each part of the project as I move forward

Thanks for the feed back......

Tom

Hello Tom,

It's always nice to see someones design evolve - I'll keep looking.

MK

Well I started to setup the model for the RS232

Then after a morning meeting the project was cancelled.....

I`m a little sad. I was looking forward to building an FPGA...... Maybe next time.

• Project Closed

Thanks all for the great feedback. I’m always building something. I`ll post the next project.

I like the feed back.

Tom

That's so vexing !

Hope the next project is as interesting.

MK

You guys (anyone) interested in building an industrial CPU? I already have the proto board produced but I still have lots to do and extra eyes are always welcome.

I would love some more experience on this one. 

I really need someone to make me some firmware…. Lol

Tell us a bit more - what processor, how many and what kind of IO.

Shabaz is involved in similar project but I think he has already decided on RPI as thebrain.

MK

• I wanted to start off with some simplicity and then evolve into a full industrial board.
• I used the ATSAMD21G18 this processor is great (in my view) for IIOT applications
• I love the sercom`s and the two internal DAC`s
• I also made it Circuit Python capable (I think)

The other idea I have is to componentize the architecture making easy to change processors or sensor communications  etc. That is why you see the power supplies very separate from the CPU

After proving the concept, I will make it much more appealing to the eye. I like space and lots of test points when proving concepts 

I did evolve it into a concept board already.... To much Coffee! (not produced). Need to prove the basics first.

That get your interest?

Anyone work with this CPU before? I`m having a *** of a time with the boot loader and firmware?

T