ftdi serial communication

[cosminnci]

Hi,
I made a pcb of the design in the image, it is a usb to 1 wire converter with a ft232rl and ds2480B.
the usb is detected, the ds2489B is comunicating partially, but not reading the sensors, I debugged till got to the  uart part where the txo line looks bad.
what could cause this? I tested connecting the ftdi to a second ftdi and sending data, all looks ok.

thank you
regards,
Cosmin

[Psi]

You have tx going to tx and rx going to rx.
A tx pin on an IC is always a transmitter ie output.
edit actually I think you have it right, that ds2480 chip looks to have tx rx inverted internally. Weird

Also, are you feeding 3.3v into the 3.3v output? It has its own 3.3 reg so doesn't need/want that.

The scope pic looks like a grounding issue

[cosminnci]

the 3,3v is only a breakout, it is not used. the ds needs 4.5-5v

[Psi]

What is the sensor ?

[Monkeh]

the 3,3v is only a breakout, it is not used. the ds needs 4.5-5v

No, it doesn't.

[Psi]

Where is vccio connected to?

[cosminnci]

The sensor is a ds18b20.
I mean I do not use the 3.3v from the ftdi, I placed the pads for testing only.
I made the same circuit on a breadboard and works.
something on my design is wrong, and I think on the ftdi part.
the ds is on the breadboard and the ftdi is on the pcb, and I get the tx line like in the image.

vccio is unconnected..

[Monkeh]

... Well you need to connect vccio or it has nothing to drive the outputs with.

[cosminnci]

I use the 5v from the usb directly

[Psi]

Vccio powers half the chip, It needs to be connected to a rail.
 3.3 if you want 3.3v io and 5v if you want 5v io

[cosminnci]

Thank you Psi, that was it, it is working now, I missed that connection.