Rapid serial data out (rsdo) backdoor enabling spi communication

A method of making a switchable-protocol rapid-data-transfer sensor array, the method comprising:

• providing a controller configured to receive serial data;
• providing a first plurality of sensor integrated circuits (ICs) connected in series and configured to wake from a low-power mode and take measurements in an active mode and to provide measurement data to the controller as serial data;
• and
• providing each sensor IC with a protocol switch configured to switch a communication protocol mode used by the sensor IC between a rapid serial data output (RSDO) mode employing an RSDO protocol and a serial peripheral interface (SPI) mode employing an SPI protocol;
• and
• wherein the protocol switch is configured to switch functionality from the RSDO mode to the SPI mode in response to a control signal from the controller,
• wherein each sensor IC includes a transducer, a shift register, and a power regulation circuit configured to selectively supply power for the low-power mode and the active mode, and an SPI clock (SCLK) pin for receiving an SPI clock (SCLK) signal from the controller, wherein for the RSDO mode, each sensor IC includes a serial-data-in (SDI) pin, a serial-data-out (SDO) pin, a bi-directional chip select (CSN) pin, and wherein the controller is connected to the CSN pin of each of the first plurality of sensor ICs by a first CSN line configured with a pull-up resistor, and wherein the controller is configured to provide a clock signal on the SPI clock (SCLK) pin to initiate serial transfer of data from each of the shift registers of the first plurality of sensor ICs to the respective SDO pins for data transfer to the controller.