help with a 232 circuit.

I've got a Radio for a RC multicopter that can output rs232 information from the muticopter. I connected it to my arduino through a TTL converter and this: library, low and behold I was getting information from my copter. I'm also using a Xbee to get some info too. So I decided to create a shield.

Attached are pictures of the schematic, layout, and the actual shield. Currently the shield isn't getting the information to the arduino correctly. I've missed important details in some previous projects. The first question that I have is did I orient the caps the right way on the actual shield? If that isn't the issue then the next question is when I run this code inside my sketch:

  if (Serial2.available()) {
    char c =;
    //Serial.println("Stuff from TX");
    //if (frsky.update(c)) { // frsky_update() returns 1 if a complete packet was successfully decoded, otherwise 0
    Serial.print("TX RSSI: ");
    Serial.print("Telemetry RSSI: ");
    Serial.print("RX Voltage: ");
    Serial.println(frsky.getRX_a1()*0.0517647058824); // The internal sensor has a 4:1 divider, so the value is 0-13,2V in 255 steps or 0,052V per step
    Serial.print("A2 Voltage: ");
    Serial.println(frsky.getRX_a2()*0.0129411764706); // A2 without divider is 0-3,3V in 255 steps or 0,013V per step

As soon as I fire up the Rx this is what repeats with the above code.

Telemetry RSSI: 0
RX Voltage: 0.00
A2 Voltage: 0.00

When I include the if statement I dont get anything to the serial monitor.

Any input as to why the information being sent to my transmitter isn't being communicated correctly would be greatly appreciated!


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Sorry to say Loren it does not look to be wired up correctly (assuming your using a MAX3232E) another capacitor should be connected pin 6(V-) and GND (note the polarity needed)
I have not checked the layout

I think I used the sparkfun site as a guide. This is what I based my circuit off of:

Are you saying that I need to add another cap between pin 6 (+) and gnd (-)?



All the reference designs in the datasheet show 4x capacitors (see below). Not sure about the sparkfun design for V+ & V-. After checking the layout I also don't see VCC connected to pin 16.