RS232 Comm with USB to TTL

Go To Last Post
3 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Hey all,

I been working on a program which takes readings from an analog sensor and relays this information to the PC terminal (br@y's terminal to be exact). I was using a USB to RS232 converter (PL2303 clone) and the program was working as expected.

I've decided to use a USB to TTL converter for the serial communication, and now am having issues with receiving communication from the mcu. There is no response whatsoever, which would lead me to believe there is an issue with the signal being sent from the converter. I've also switched the RX/TX lines as apparently there has been a silk screening faux pas on these converters.

Both the RX and TX pins off of the converter have 3.6V. Connecting RX and TX produce an echo of the character that is sent.

I've attempted to connect an o-scope from ground to TX while sending a character via the PC's terminal, and the pulses on the o-scope show up infrequently, and when they do, the waveform is more sinusoidal than square. The peak voltage of the waveform is 3.6V.

Setup Info:

ATMega168
external clock (16MHz)
baud rate = 9600
Vcc = +5V
Link to the USB to TTL I had purchased:
http://www.ebay.com/itm/32137885...

Driver being used for the converter is the CP2102 v.6.7 directly from Silicon Labs

Thanks,
Ben

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

What happens if you disconnect it from the mcu (and power it from USB). Do any of the LEDs turn on and/or flash when you send data to it from the PC?

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

There is a TX LED on the converter which lights up when I send the data from the PC.

Something I have noticed with the terminal is when I hit the "COM" button, with the working USB to RS232 converter there would be a hex signature after the "USB->COM adapters: ". When I hit the "COM" button using the USB to TTL converter, there is no signature displayed. I've attached a screen shot of what I'm referring to.

Attachment(s):