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July 8, 2010
about 3 years ago
I realize that this is far removed in time from the original post, but I thought I might add a note for users with similar issues:
A relatively painless option for changing the resistor divider in question, regardless of which board revision you have, is to add resistors either in parallel with the either the ‘top’ resistor (from RX_HV to RX_LV) or ‘bottom’ resistor (from RX_LV to GND), (off of the break-out board). This approach effectively lowers the resistance of either the ‘top’ or ‘bottom’ resistor, shifting the output voltage up or down respectively.
A similar approach could be used to ‘speed up’ the ‘pull-up’ on the TX side(s) with either of the the pull-up resistors, or using a similar suggestion to (b) above the pull-ups on the TX lines could be ‘slowed’.
about 5 years ago
The problem you’re encountering, (though it’s been a while so I bet you’ve figured it out already), is that the TX lines are pulled high, (through pull-up resistors on the board), anytime that nothing is acting to pull them low. Floating inputs will go high because of this, which is the intended behavior. Pulling the TX-line low on either side will cause the other side to properly transition to a low state.
The device you refer to only passes the signal in one direction, from the ‘A’ side to the ‘Y’ side, so it wouldn’t be useful to communicate information back the other way. Applying a signal to the ‘Y’ output side does not affect the state of the ‘A’ input associated with it.
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