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Why do I get unpredictable UART results with my Synergy SSP design?

Latest Updated:09/12/2016

Question:

I seem to get some unpredictable results with my UART implementation using SSP. What might be going on?

Answer:

The RS-232 transceiver connected to the UART port in the Synergy MCU will automatically go to 'sleep' after 30 seconds of inactivity to save power. In order to give it time to 'wake up' you might 'spike' the connection by sending a few spaces with a carriage return before sending actual data.

Another issue might come up on the SK-S7G2. Note that on the kit an external ICL3227 is used to 'buffer' the serial output. The sleep mode is set via a pin 'strap' that is on pin 12 of U7 (the ICL3227) on the SK-S7G2 Kit. This input can be tied to 3.3V (pin 15 or 16 on U7- the ICL3227) if you want to disable this feature. This requires hardware modifications on the board however, so it may not be a desirable option.