The The finished board. I have tested everything but the receive circut by using UBW Play.bas to toggle processor pins

There are a few minor things that did not go right. The most obvious is that the resistors are too long to fit between the holes. The large blue 4 position connector has pins on .2 inch centers. The layout is .1 inch centers. To fix that I drilled new holes and jumpered to it.

I did not populate the switches or ICSP connector.

3v0

I have one of those little Dremel drill-press stands (you bolt the dremel-tool, or in my case the knockoff dremel-like tool, into it). It makes drilling the PCB holes go much faster.

hallo everybody !
I am very excited about this project ! I love you all ! My english is quite bad, but my programmer's skill are not. Very soon I will complete firmware for USB to RS485 convertor and you will be first to know !

Love you !

you can download full project code for FW - USB to RS485 / RS232 converter on this site:

http://free-vt.t-com.hr/maca64/

IMPORTANT NOTE: I have no test hw so this is very, very BETA version ( not tested at all ! )

THANKS to Brian !
THANKS to 3v0 !

I got my HW, let's rock !
I will describe every step, including mistake I made, it may help someone else. I got PIC with Brian's bootloader in it.

First mistake: I did not press PROGRAM button, and bootloader did not start. when I did it, everything is OK !

Second mistake: when Windows report new hardwer, I pointed to CDC inf file !

That was wrong, you must select inf that come with Microchip PDFUSB ( bootloader app. ). Finaly I started PDFUSB and load my Firmware into PIC. When I reset board, Windows report new hardware. This time I pointed to CDC inf and it works ! I started HyperTerminal and connect to COM7.

Third mistake: my board was connected to COM8 !

You must verify that in Control Panel -> Ports ! On my PC there are COM7 and COM8. First is dedicated to bluetooth, and second is good one ! Finaly I wrote V ( CR ) in HyperTerminal and magic happend - I got response FW kepica C v1.3 !!!

That will be enough for first time !

kepica,

That is AWESOME news! Way to go. I hope to be updating the main UBW website soon to make some of these things much clearer - which INF file you need and when, which button to push and when, what the bootloader really does, etc. etc. Hopefully others can learn from your work and it can become easier for all.

Let us know how the testing goes.

*Brian

my work is in progress. I am satisfied.
NOTE to 3V0 - choice of opto is important. you can not use 4N37. you must select one with faster on-off time !

important Error in 3V0's shema:

on RX line opto ( pin 1 ) must be connected to pull-up resistor, not pull-down !!!

(i.e. to 5V not to the ground !!! )

I am finished ! it work's !!!!

more details next time !!!!!!!

first of all - my website ( see link above ) is NOT updated. please be patient, I will update it very soon, so you can download tested version of my project.

few more details, about my work: I connect my PC to Siemens S7-222 PLC via MODBUS protocol. My firmware in PIC accept parameter from PC that correspond to MODBUS commands - read / write coils, registers etc. On each parameter PIC create packet and transmit it via USART to RS-485 bus. When PLC transmit response, it is accepted via USART RX interrupt procedure, and send forth to PC.

NOTE to 3V0 - you have one more error in your schema - resistors in series with LEDs on RX, TX, TX_EN lines has to be bigger.

kepica,

School is about over here and I will have time to work on this project.

What opto isolators did you end up with?
What was the max baud rate you tested?

Will fix the schematic and layout a new board.
If you have any other suggestions regarding the board I am would like to hear them.

Change OK1 pin1 to connect to VCC/2 via 10K pullup
Changed R16, R17, R18 from 470 to 680 Ohm.
Moved the jumper from under the PIC to an easier to solder location.
The Opto Isolators still show 4N37 till I know what should replace them.
Changed the RS485 connector to a .2 inch spacing.
Will post new board soon.

The board has been layed out with the needed fixes. It has also been made easier to etch and solder.

The UBW_RS485 layout is created with somewhat low quality DIY etching in mind. It can be etched as a single sided board with 3 jumpers or as a double sided board with 6 vias. There are no traces between pads less then .2 inches apart. To make soldering easier pads are large (restring 45%) and the space between copper has been increased form 8 to 10 mil.

I will post again after the board is constructed and again when I try RS485 enabled software.

hello everybody!
I updated my web page ( see link in my post above ). There is tested version of my project. This is not a commercial version that I am really doing now, but it works fine, so you can do whatever you wont with it.

IMPORTANT NOTE - you can not use this project with Brian's bootloader, instead you have to change config bits to get 32 MHz clock ( there is one thread about this topic on this forum )

Kepica,

The link Download complete Project ( ZIP )
http://free-vt.t-com.hr/maca64/FW_RS485.ZIP
seems to be broken.