An apparatus and method are described for implementing efficient communication between a microcontroller and a communication module. For example, one embodiment of an apparatus comprises: a secure communication module to establish a secure communication channel with an IoT service; and a microcontroller unit (MCU) to execute application-specific program code to implement an application-specific function of an Internet of Things (IoT) device; a serial peripheral interface (SPI) bus to communicatively couple the secure communication module to the MCU; and a control line residing in a first state or being transitioned to a second state by either the MCU or the secure communication module, wherein when performing a transaction over the SPI bus, either the MCU or the secure communication module is configured to transition the control line to the second state, thereby informing the MCU or the secure communication module that a transaction is occurring, wherein upon completing the transaction, the MCU or the secure communication module is configured to release the control line, thereby allowing the control line to transition back to the first state.