Trouble with FT232

I made FT232 USB <-> UART converter, but it wasn't working properly. I used schematic from datasheet figure 6.4. But it wasn't working properly. error A request for the USB device descriptor failed. appeared each time I connected converter with jumper on voltage level selector (without jumper everything was ok). Afer some online search I found solution on Ketturi electronics. I simply forgot to connect Test (pin 26) to ground.
So if you have issue with FT232 descriptor check first if test is connected to GND.

Second thing I found, is that FT232 has configurable max current drown from USB port (new chip had  configured100mA). To check/change value you have to download FT_PROG. Open it, scan for connected devices (F5). You can see or change max current in USB Config Descriptor category. Also in Hardware Specific > IO Controls you can change CBUS pins purpose for:
  • RxD LED
  • TxD LED
  • RxD/TxD LED (one for both)
  • Clock for your uC 6/12/24/48 MHz
  • some other stuff I didn't bother to understand fully: SLEEP#, PRWEN#, I/O MODE, TXDEN, WR#, BitBang WRn, BitBang DRn (@Edit SLEEP# tells your uC that USB is in sleep mode)
After changing some stuff you have to program EEPROM (Ctrl+P).
This will allow you to feed more current to your project.
All of this stuff is widely descripted in FT232R datasheet.

I attached  IMO optimal schematic for FT232 adapter for AVRs and Arduino boards or chips. It has auto reset (DTR line with cap) needed for automatic sketch upload and LEDs for Tx and Rx. It also has Vcc selector (5V/3V3/external) for Tx and Rx and uC's Vcc, but remember that datasheet says: "Up to 50mA can be drawn from this [3V3OUT] pin".


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