- Fri Feb 05, 2010 8:29 am
#92787
There is a design flaw with the XBee Explorer Regulated (WRL-09132). There is a diode in series with the UART data input pin, causing a 0.6 Volt potential drop (like all diodes...). Well, if you hook up a standard 3.3 Volt logic to this input, it may barely work (although, its still bad engineering practice and will destroy your noise margin on your logic input). But many 3.3 Volt devices, such as my San Jose FV-M8 GPS have a 2. 8 Volt logic level output. As such, the 0.6 Volt diode drop lowers the logic level right into the "forbidden region" and the XBee just sends out garbage.
Desoldering the diode and replacing it with a wire fixes everything, and the TX/RX LEDs still work.
Anyway, point is, you can't just put diodes in series with logic inputs without causing all sorts of noise and compatibility problems.
Desoldering the diode and replacing it with a wire fixes everything, and the TX/RX LEDs still work.
Anyway, point is, you can't just put diodes in series with logic inputs without causing all sorts of noise and compatibility problems.