April 20, 2024, 06:19:05 AM

MOD-USB-RS232 problems

Started by hnlk, February 04, 2013, 02:00:11 PM

Previous topic - Next topic



The short version: I can not receive data on the PC via my MOD-USB-RS232 board.

The longer explanation:

My setup:
A MOD-IO AVR board connected via the UEXT port to a MOD-USB-RS232 board to a PC. The PCB "jumpers" on the MOD-USB-RS232 board are set so UEXT pin 3 (RXD on AVR) is connected to TXD on the PIC, and UEXT pin 4 (TXD on AVR) is connected to RXD on the PIC.

On the MOD-IO AVR board I send a text string via the UART, but nothing is received on my PC.

I have installed the MOD-USB-RS232 board with the drivers from the Olimex site, and it shows up as a COM port. The LED on the MOD-USB-RS232 board flashes when connected to the PC.

To verify that I really transmit something from the MOD-IO board, I have connected it to the MOD-RS232 board and directly to a RS232 COM port on the PC. This way I can see, that data is transmitted correctly.

The transmission speed is 9600 baud.

If I transmit a character from the PC via the MOD-USB-RS232 I get the message "UEXT test ERROR!" back. After that, the LED on the MOD-USB-RS232 board is on constantly.

I take it for granted, that the PIC on the MOD-USB-RS232 comes with its software allready flashed into it, so I can use the board without putting firmware into the PIC.

Can someone give me a hint?



This is not an answer to your question, maybe i get the same problem
or find anything else worth to tell it her.
First I  want to know is this correct; you wrote:
The PCB "jumpers" on the MOD-USB-RS232 board are set so UEXT pin 3...
does this mean you soldered the 2 '3 copper plates# on the back side of the

regard barry


That is correct: I have soldered pin 2 and 3 on the copper plates together for both "jumpers".



... and then, did you cut the 'original' connections?
I think, you also have to do this.
I want to connect MOD-EKG to PC via MOD-USB-RS232 and i do it like in
the manual:"Connecting MOD-EKG to PC via MOD-USB-RS232 board.pdf"
and an answer from Olimex was:
The default SMT jumper position has to be cut with a sharp cutter knife
and then you have to solder the jumper in the other position. The issue is
caused by the fact that both boards were planned as extension boards
(configured both as devices) and RX and TX lines collide.
All together in the manual above it is written:
Before connecting MOD-USB-RS232 to MOD-EKG, several MOD-USBRS232'
s jumpers must be changed from theirs default state!
These jumpers are as follow:
- 4_TX/4_RX must be changed in position 4_RX(2-3 closed);
- 3_RX/3_TX must be changed in position 3_TX (2-3 closed);
- UEXT_PWR_E have to be closed! This enables MOD-EKG power supplying
via USB when its switch BAT/UEXT is in position UEXT. So in this case
we're going to supply MOD-EKG via USB instead of BAT which also is

Question: Do you also have such a manual for your installation and must
the UEXT_PWR_E also be closed?




Hi Berry,

Thank you for your input. The document you refer to is a nice one. I have not seen it before. There is only a very short and not so informant manual for the MOD-USB-RS232 board on its site on the Olimex site.

I have checked the 3_RX/3_TX and 4_TX/4_RX jumpers and I could actually measure that pin 1 and 2 was shorted. Visually it does nok look that way. But now I have cut the track between pin 1 and 2 for both jumpers.

I have not closed the UEXT_PWR_E as I do not need to supply the MOD-IO board from the MOD-USB-RS232 board. I have also not closed the USB_PWR_3.3 as I cannot find any info on what that does.

I still get the "UEXT test ERROR!" message when sending chars to the MOD-USB-RS232 board from the PC side, and I do not recieve any data from the MOD-USB-RS232 board.

So, maybe the board is defect?



Hey guys,

The problem: It seems between 15 and 20 MOD-USB-RS232 boards have left the factory without being programmed with the final shipping firmware (USB – Serial convertor one); they were shipped with the testing program.

The solution: If you have compatible PIC programmer (like PICKit3) for the small 0.05'' ICSP connector you can reprogram it with the Prebuilt.hex which might be found in the package on the devices web page. Direct link: https://www.olimex.com/Products/Modules/Interface/MOD-USB-RS232/resources/Demo_MOD-USB-RS232.zip. If you don't own such a programmer it would be good idea to borrow from a friend/colleague/retailer (if you purchased it from a retailer – kindly ask them for the reprogramming favor). We will reprogram the board free of charge but our return policy doesn't cover shipping expenses. The full return policy might be found below:

Warranty and returns:

Our boards have lifetime warranty against manufacturing defects and components.

During the development work it is not unlikely that you can burn your programmer or development board. This is normal, we also do development work and we had damaged a lot of programmers and a lot of boards during our daily job so we know how it works. If our board/programmer has worked fine then stopped, please check if you didn't apply over voltage by mistake, or shorted something in your target board where the programmer was connected etc. Sometimes boards may be damaged by ESD shock voltage or if you spill coffee on them during your work when they are powered.

Please note that the warranty does not cover problems caused by improper use, short-circuiting, over-voltages, ESD shock etc.

If the board have warranty label it should be not broken. Broken labels void the warranty, same apply on boards with intervention by customer like additional components soldered or removed components, such boards will be not subject of our warranty.

If you are positive that the problem is due to manufacturing defect or component you can return the board back to us for inspection. When we receive the board we will check and if the problem is by us we will repair/replace free of charge, otherwise we can quote on the repair cost.

Note that all shipping back and forth is to be covered by the customer.

Before you ship anything back you need to ask for RMA.

When you ship back please attach to it your shipping address, phone, e-mail, RMA# and a brief description of the problem. All boards should be sent back in antistatic package and should be well-packed to prevent damage during transportation.

In future the test and the demo program will be bundled together so situations like this won't occur.

Sorry for the caused inconvenience.

Technical support and documentation manager at Olimex