A method for transferring data during power transfer in a wireless power transfer system , wherein the wireless power transfer system comprises a power transmit device arranged to transfer power over an inductive wireless power transfer interface operating at a transmit frequency (f TX ) to a power receive device , the wireless power transfer system being adapted to transfer information at half duplex using Frequency Shift Keying, FSK, in one direction and Amplitude Shift Keying, ASK, in the other direction, the method comprising: transferring , at the transmit frequency (f TX ) by the power transmit device , power to the power receive device and, during the transferring : transmitting , at the transmit frequency (f TX ) by one of the power transmit device or the power receive device , a first data packet to the other of the power transmit device or the power receive device using one of two modulation types being FSK or ASK and, during the transmitting : determining , by the device transmitting the first data packet, if a signaling condition relating to the transmission of the first data packet is fulfilled, wherein determining if a signaling condition is fulfilled comprises evaluating a modulation accuracy of a signal comprising the first data packet and if the evaluated modulation accuracy is lower than a modulation accuracy threshold, the signaling condition is determined to be fulfilled, and if the signaling condition relating to the transmission of the first data packet is fulfilled, changing a data communication configuration of the device transmitting the first data packet. transferring , at the transmit frequency (f TX ) by the power transmit device , power to the power receive device and, during the transferring : transmitting , at the transmit frequency (f TX ) by one of the power transmit device or the power receive device , a first data packet to the other of the power transmit device or the power receive device using one of two modulation types being FSK or ASK and, during the transmitting : determining , by the device transmitting the first data packet, if a signaling condition relating to the transmission of the first data packet is fulfilled, wherein determining if a signaling condition is fulfilled comprises evaluating a modulation accuracy of a signal comprising the first data packet and if the evaluated modulation accuracy is lower than a modulation accuracy threshold, the signaling condition is determined to be fulfilled, and if the signaling condition relating to the transmission of the first data packet is fulfilled, changing a data communication configuration of the device transmitting the first data packet. determining , by the device transmitting the first data packet, if a signaling condition relating to the transmission of the first data packet is fulfilled, wherein determining if a signaling condition is fulfilled comprises evaluating a modulation accuracy of a signal comprising the first data packet and if the evaluated modulation accuracy is lower than a modulation accuracy threshold, the signaling condition is determined to be fulfilled, and if the signaling condition relating to the transmission of the first data packet is fulfilled, changing a data communication configuration of the device transmitting the first data packet. <EOS>