The modules TEI0015 and TEI0016 implements a handler for executing commands. The serial interface speed
must be set to 115200 bits, commands consists of a single  character in UTF-8 encoding.
Each command must be transmitted individually.

These commands apply since module revision 03.

"1"   Sets the pre-amplification of the ADC's input to 1. Firmware dependend

"2"   Sets the pre-amplification of the ADC's input to 2. Firmware dependend

"4"   Sets the pre-amplification of the ADC's input to 4. Firmware dependend

"8"   Sets the pre-amplification of the ADC's input to 8. Firmware dependend

"r"    The ADC measure once and transmits this value

"t"    The ADC measures 1 mega samples and saves the values into its SD-RAM

"."     A single value of stored ADC measurment is transmitted

"+"   128 values of stored ADC measurements are transmitted

"*"    16 kbit values of stored ADC measurements are transmitted

"x"    Instead of ADC values the value "12345" is stored 1M times in RAM, values are transmitted via ".", "+" and "*"

"y"    Instead of ADC value, hexadecimal values, in ascending order, are generated and stored into the SD-RAM,
        the values are transmitted in via "." ,  "+" and "*"

"z"   The value "12345" is generated and direct transmitted 256 times

"?"   The module returns its ID:
               TEI0015 with ADC AD4003 / 2 MSps returns "1"
               TEI0016 with ADC ADAQ7988 / 0.5 MSps returns "2"
               TEI0016 with ADC ADAQ7980 / 1 MSps returns "3"