[Gumstix-users] [help]summit ttyS0 Tx voltage level become 0V

[tomason <tom...@12...>]

Hello all,
I use the summit(and overo air) connect to avr micro-controller by ttyS0s, the logic level of ttyS0 on avr has changed to 1.8V. When I connected them together, 
run my program to send message from overo air to avr，the voltage level of ttyS0's Tx changed to 0V, and the Rx of it can't receive any signal from any other 
device's Tx because of the voltage level can't reach 1.8V. Is there any wrong operation for the settings of serials, how to make the voltage level back to normal?
Any help would be great appreciate.
Best regards