Dynamic decoding of communication between card reader and portable device

A portable electronic device configured for decoding an encoded data signal received at an audio interface of the portable electronic device the portable electronic device comprising:

• an audio interface configured for receiving and encoded data signal encoded with an adjustable encoder clock frequency and
• processing circuitry adapted to:
• pre-process the received encoded data signal;
• scan the received encoded data signal for a known start sequence;
• when no known start sequence is detected, request adjustment of the adjustable encoder clock frequency and repeat the step of scanning the received encoded data signal for a known start sequence until a known start sequence is successfully detected;
• when a known start sequence is successfully detected;
• estimate an actual frequency of the received encoded data signal based on the detected start sequence;
• interpret, a data block succeeding the start sequence using the assessed actual frequency;
• and
• assess whether the interpreting of the data block was successful;
• and
• when interpreting the data block is unsuccessful, request adjustment of the adjustable encoder clock frequency.