Pullup on UART2_RX line should only be connected to +3V3

[scdwyer]

The 10k pullup on UART2_RX (R26 on lisa/M v2.0) I believe should be connected directly to +3V3 and NOT to U2_POW. UART2 is not 5V tolerant so if you switch that jumper to power an external something with VIN you will also put VIN on UART2_RX, even if the device attached has an onboard reg to bring it back to 3V3 or otherwise has 3V3 levels.

Is this valid?

[dewagter]

I believe you are right. You can reasonable hope that the stm32 clamping
diodes will survive the very low current drawn by the 10k so it should not
be damaged if you did configure uart2 at 5V or more.
On May 7, 2012 3:32 PM, "scdwyer" <
[email protected]>
wrote:

The 10k pullup on UART2_RX (R26 on lisa/M v2.0) I believe should be
connected directly to +3V3 and NOT to U2_POW. UART2 is not 5V tolerant so
if you switch that jumper to power an external something with VIN you will
also put VIN on UART2_RX, even if the device attached has an onboard reg to
bring it back to 3V3 or otherwise has 3V3 levels.

Is this valid?

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