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I have a HDD which has serial access but needs 1.8v TTL serial. I only have 3.3/5v serial devices. The standard PL2303, A UART Usbbee, and a generic serial adapter. The PL2303 & generic have 3v/gnd/txd/rxd/5v pins and the USBbee is pictured below.
I found some LM1117 regulators which can take in 3-12v and have 1.8v output.
Is there any way I can modify the generic adapters or the USBbee with the regulator to enable reading of 1.8v serial? 
Pin 4 of the PL2303 or FT232R SOIC package is VDD_325/VCCIO, the Serial level voltage input. If you inject 1.8V there, the serial UART pins will be at 1.8V TTL levels.
http://www.prolific.com.tw/UserFiles/files/ds_pl2303HXD_v1_4_4.pdf http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT232R.pdf
The UARTSBee V4 uses the FT232R or a clone.
http://wiki.seeedstudio.com/UartSBee_V4/
By removing the 3.3V/5V switch on the lower right corner, and injecting 1.8v to the middle pin, you could make this a 1.8V serial adapter.
