UbiSwitch UART communication issue

– Copied from customer email –

Just testing the UbiSwitch module and trying to get the UART working, but all I’m getting so far is the screen below, every time I apply 12V to the module:-

We use a lot of FTDI USB to serial adapters that usually work really well.

Referring to your UbiSwitch Software Guide the required settings for the UbiSwitch module, happens to be what I normally use, see below….

Using a scope the Tx/Rx lines seems to be connected correctly and puts out a pulse of Tx data as power is applied.

Tried changing some of the settings incl baud rate but the settings above seem to work best.

Is there anything else you might be able to think of?

Whats the part number of the FTDI USB converter you are using?

– Copied from customer email –

Hmm… That’s RS232. This is TTL level serial (3.3V and GND).

That won’t work with UbiSwitch, needs to be TTL level serial.

I’m worried you may have fried the chip on UbiSwitch. It does still appear to be outputting which is good. Do you have a TTL level serial to USB converter?

– Copied from customer email –

Strange if that’s the reason, as all of the designs I’ve done over the last 10/15yrs o/p a 3.3V RS232 signal and that works fine with all of the FTDI USB converters we have?

The recommended converter in your data sheet actually uses a FTDI device…. Moyina USB to Serial Converter, USB to TTL Adapter for Development Projects - Featuring Genuine FTDI USB UART IC ‘FT232RL’: Amazon.co.uk: Computers & Accessories

Do we know the voltage output swing on your converter? On the datasheet of the part you’re using, it looks to be ±5V, which would not be compatible with the 0-3.3V swing.

This is different to the output of the TTL UART converter we specify.

It is worth clarifying that RS232 is not the same as TTL serial. TTL serial is single-ended, typically 0 - 3.3V or 0-5V. RS232 is typically ±5V (though it can swing as much as ±15V, though not from a USB powered converter), so it swings below 0V.

I’m 90% sure this is the issue. It’s a pretty common confusion. The UART pins on UbiSwitch interface directly with the pins of a 3.3V microcontroller. So it’s not a RS232 signal, it’s a TTL UART signal.

– Copied from customer email –

That makes a bit more sense if you are saying the UbiSwitch module doesn’t have a RS232 chip to convert the uProc UART signals…

I’ll see if I can order Moyina Amazon converter then….

Yes that’s right, apologies I should have been clearer. It’s not RS232.

Let me know how you get on.