Need help with FT232RL

Hi
I recently designed a USB relay controller, and I have the prototype boards in my hand.

USB communication was intended to achieve through famous FT232RL chip.

I have soldered the MCU and FT232 and found out it is not working.

then I tried to see if FT232 is working properly by connecting RX to TX and doing echo test. test was a fail

Then I connected my logic analyzer to TX pin (pin 1) of FT232 and tried to capture its output while sending serial characters through USB.

according to the logic analyzer , output of FT232 is incorrect.

it lowers its output for the full length of the character and then set to high. this is same with any character.

then I tried changing chips but ended up with same result.

I have attached analyzer output and the schematic here.

Is there anything I'm doing wrong here? (this is my first time with FT232) any configurations needed?
or am I a victim of counterfiet ICs? (brought FT232 from chinese seller) (but FT_PROG can read and write FT232 chips EEPROM)

(LEDs are connected incorrectly, i noticed it after production of prototype boards. but I dont think that is the reason for this coz I checked the output after removing those LEDs)



Thanks.

VCCIO only needs to be connected for the correct voltage level, 3,3 or 5 volts... why the inductor coil ?

btw. try also without connecting de 2 leds, had read somewhere these had side effect on working...

Look at page 24 of the ft232rl datasheet. You don´t have the reset connected to the USB V+ like you should, the device needs to be reset on the exact moment you plug in the usb cable, otherwise the negotiation will not work.
Or if you need it to be isolated from other circuitry based on those optocouplers, then use the schematic from page 23 and power everything from the bus.
Also you seem to be missing a pullup on the RX side of the optocoupler.

thefug said:

VCCIO only needs to be connected for the correct voltage level, 3,3 or 5 volts... why the inductor coil ?

btw. try also without connecting de 2 leds, had read somewhere these had side effect on working...

Click to expand...

it is not inductor coil. it is a ferrite bead, for filtering

tried without 2 leds. but no luck

kubeek said:

Look at page 24 of the ft232rl datasheet. You don´t have the reset connected to the USB V+ like you should, the device needs to be reset on the exact moment you plug in the usb cable, otherwise the negotiation will not work.
Or if you need it to be isolated from other circuitry based on those optocouplers, then use the schematic from page 23 and power everything from the bus.
Also you seem to be missing a pullup on the RX side of the optocoupler.

Click to expand...

I will try reset line pull up

I tried after disconnecting "reset" pin from vcc and left it unconnected. but result is the same.

any suggestions?

Did i say leave reset unconnected? No, I said connect it the exact same way as on page 24.

kubeek said:

Did i say leave reset unconnected? No, I said connect it the exact same way as on page 24.

Click to expand...

hi
configuration I'm using is bus powered configuration. it is on page 23. it has reset pin not connected

Sorry, my bad. Then it should work if you have all the connections right, all pins soldered properly etc. Does the pc recognize that you plugged the device? Do you get 3.3V on the 3v3out pin? Do you have the blocking cap connected there?

kubeek said:

Sorry, my bad. Then it should work if you have all the connections right, all pins soldered properly etc. Does the pc recognize that you plugged the device? Do you get 3.3V on the 3v3out pin? Do you have the blocking cap connected there?

Click to expand...

PC recognize it as FT232 usb to uart.
I cannot check 3.3v now. i will check and tell you tomorrow.

Problem solved.
I brought 2 FT232RL from another source and they worked perfectly.
It seems all FT232 ics I brought before are damaged products.

Thanks everybody for the help