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TM4C1294 analogRead() and Ethernet failure

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I'm having a few issues with this simple sketch:

#include <Ethernet.h>

EthernetClient client;
int sensorPin = A3;
float sensorValue = 0;

void setup() {

void loop() {
  sensorValue = analogRead(sensorPin);

The ADC values seem to jump around randomly when Ethernet.begin(0) is called.

If I comment out the Ethernet portion the ADC seems to be stable again.

I've tried other analog input pins and I get the same result.


Hardware is a Connected LaunchPad (EK-TM4C1294XL) + LM35 sensor, both from TI.


Any ideas?



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here are a few samples of the sensor: http://pastebin.com/WDLhm0v0


As you can see there's way more variance in the second column, which is samples taken after Ethernet.begin(0);


Samples with Ethernet disabled range from 265 to 287 (acceptable, within specs of the sensor) while samples with Ethernet enabled range from 127 to 368 (way off).



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