ADC drop outs with AnalogBinLogger about sdfat

[greiman]

I have no idea what you mean by logging a working serial connection. What is your hardware setup?

I test by logging a sine wave and analyzing it. See this DATA.png in the AnalogBinLoggerExtras folder.

The 2000 Hz sine wave is reproduced correctly.

[cmteuffel]

Thanks for your fast response. I'm aware that you've comprehensively tested the library and I read from your AdcErrorStudy.txt that you went quite some trouble to test the ADC. I simply used the library using the default settings in a real world hardware setup (e.g. USB powered UNO).

Towards my hardware setup:
I have a serial loop back connection, simply receiving the sent data (ASCII) at the same PC. Therefore I know the connection is working and what's been sent when. I've put a resistor in the connection line and measure DC above this resistor while sending using the UNO contacts A0 and A1.

Occasionally, the logger reads no voltage (series of zero values). At times, this drop out happens when there should be a voltage spike. So, while for example a character "1" (00110001) was sent and received using picocom, the same character is "!" (00100001) in the log file. This is, because one complete voltage spike was cancelled. These ADC drop outs seem to be randomly distributed. I could reproduce the behaviour with a Mega 2560.

If this is because of my hardware setup, should'nt the drop outs also be visible at the terminal output? Maybe the default settings are the issue.

[cmteuffel]

I just tried a different cabling and made another log attempt just to be sure. The results are similar.

[greiman]

I setup a second Arduino with several programs that send serial. I have no problems.

Here is a typical program that sends a serial signal.

void setup() {
  Serial.begin(1200);
}
void loop() {
  Serial.write(0);
  Serial.write(1);
  Serial.write(2);
  Serial.flush();
  delay(10);
}

I connect digital pin 1 of the sending Arduino to analog pin 0 of the logging Arduino and log at 5,000 samples per second for a long time.

Here is a plot of a small part of one of the log files.

Note the 0, 1, 2 pattern. This is Arduino 8-bit no parity serial. I assume you understand serial data format.

I can't help you more since I can't reproduce your problem.

Edit: I hope you are not truly trying to log RS-232 levels.
https://www.sparkfun.com/tutorials/215