ESP01 flashing error
Your wiring sounds wrong.

Tie CHPD to Vcc (3.3v) to enable the device. 

Tie GPIO0 to ground as you power up, to put it into programming mode. 

RST can be left floating, or PULL (not tie!) up to Vcc through a resistor, say 10k.

That diode level shifter arrangement is unusual. A potential divider on the ESP's RxD is all you need - say 1k and 2k.