My WP-34S : USB to Serial cable prototype

[olr]

Hi,

i'm also waiting for pogo pins to get my cable ready (no extra LEDs though). I'm not an expert in electronics but i have some questions/remarks.

• You are connecting 3.3V to Vcc of the calculator. This is probably neccessary when the batteries are removed. But what if not?
• The RESET pin is already high(3V). I think a reset of the calculator is triggered when the RESET pin is connected with GND?
• My USB-TTL converter is also based on Prolific PL2303HX and TX/RX are operating at 3.3V and it has an 3.3V output pin, that might be used.
  

Usually FTDI chips are recommended. However i flashed my HP20b successfully with a PL2303HX-based converter.

olr