What is the default configuration for the pins/GPIOs during shutdown, and during/after power-up on the Si4x55, Si4x6x?
The table below describes how the pins and GPIOs are configured during shutdown (i.e. SDN pin held high), and during power-up (i.e. POWER_UP command sent and waiting for CTS):
|Pin name||Direction||SDN = High||During/After POWER_UP|
|nIRQ||Output||Pull-up||Driven high (no Pull-up) / NIRQ*|
|SDO||Output||Pull-up||SDO data or Pull-up if no valid data|
*Once the CTS for the POWER_UP command arrives (i.e. the API is successfully loaded) NIRQ goes low, and the interrupts have to be cleared using GET_INT_STATUS command.
By default, the GPIOs (i.e. GPIO0-GPIO3, NIRQ, SDO) are configured to the lowest drive strength. This means that retrieving the GPIO configuration via GPIO_PIN_CFG command right after the POWER_UP command, the chip returns 0C 08 0C 0C 27 0B 60. Note, however, that in the WDS-generated radio configurations the drive strength is set to the highest by default (e.g. GPIO_PIN_CFG 00 00 00 00 00 00 00). This is different than the chip default.