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Consider connecting level shifter EN to DAC EN #107

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whitequark opened this issue Mar 1, 2019 · 2 comments
Closed

Consider connecting level shifter EN to DAC EN #107

whitequark opened this issue Mar 1, 2019 · 2 comments
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hardware Component: hardware revC Hardware revision: C
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@whitequark
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Related to #96. We really don't need the level shifters to guess whether the IO port is enabled, and lock up the bus if it guesses wrong.

TCA9509 does this:

The TCA9509 drivers are not enabled unless VCCA is above 0.8 V and VCCB is above 2.5 V. The enable (EN) pin can also be used to turn the drivers on and off under system control. Caution should be observed to only change the state of the EN pin when the bus is idle.

which is good enough, but I think explicitly managing EN would be safer.
@whitequark whitequark added the revC Hardware revision: C label Mar 1, 2019
@whitequark whitequark added this to the Preview 1 milestone Mar 8, 2019
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marcan commented Mar 8, 2019

Sounds good to me. We still need to make sure we have something like a 100ms delay after Vio shutdown before reconfiguration to allow for plenty of time for charge to drain on revC0, but this makes revC1 more robust in the face of external capacitance.

@marcan marcan self-assigned this Mar 8, 2019
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marcan commented Mar 28, 2019

Kill it with fiiiiiiiire

@marcan marcan closed this as completed Mar 28, 2019
@whitequark whitequark added the hardware Component: hardware label Apr 16, 2019
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