Quote:
Originally Posted by knc1
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Avoid makes/models that have indicator leds on the Tx and Rx leads - geekmaster reports problems with using those that require almost as much electronics skill to modify as building one from the git-go.
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The kindle TxD cannot sink enough current to light a serial adapter RxD LED. The LED may faintly light up, but the kindle has a 1K series resistor and the serial adapter RxD will only see about 1.4v on its RxD line for a logic zero, and will think that is actually a logic one. My modification consisted of removing the LED, adding a 22K pullup resistor to +3.3v, and adding a series diode to the wire going from the kindle TxD to the adapter RxD, such that the kindle could pull the adapter RxD line down to 0.7v (silicon diode voltage drop) which is recognized as logic zero for 1.8v/3.3v/5v TTL devices.
Yes, perhaps just buying a 1.8v adapter is better, but good luck searching for one, because most 3.3v adapters come with 1.8 meter cables.
