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Assuming that you certainly have already checked the circuit schematic and layout design seeking for errors, the most likely reason for that - externally to the board - is some mistake in connecting TX/RX outside.
Show us your pcb layout.
What capacitors dud you use? Value, material.
Did you check the usb connector pinout?
Do you know it is TTL level, and not RS232 levels?
How do you test functionality?
Did you install the drivers on the PC side?
Did yoj open the port?
Did you do the correct baudrate setup in PC?
There is nothing connected to OSC1/OSC2 respectively at pins 27/28. According to the following datasheet (page 12), when operatiing the device at 3,3v it is required an external Oscillator:
Notes:
1. The minimum operating voltage VCC must be +4.0V (could use VBUS=+5V) when using the
internal clock generator. Operation at +3.3V is possible using an external crystal oscillator
I don't think external oscillator is required as it is not operating in +3.3V supply. The 3.3V shown in the layout is just the output from FT232RL IC. The opertaing voltage of this circuit must be +5V.
Problem is solved with new IC(Original IC). That IC was Chinese version, so it was not working. I can load HEX files in MCU with my designed board. It is working fine. Thank you for support.
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