9. Receiver FIFO Read Command

Reads one received byte from the receiver FIFO.

Register Fields

Unlike the configuration commands, the Receiver FIFO Read Command has no configurable fields. The transmitted byte is fixed, and the received byte contains the FIFO data.

Direction	Bits	Meaning	API
TX	7:0	Fixed command value (0x00)	—
RX	7:0	Received FIFO data	rfm12_read_fifo()

This command performs an immediate SPI transfer. It transmits 0xB000 and returns the low eight bits of the response as the received byte. It does not require rfm12_apply_to_radio() to perform the read.

Receiver FIFO mode must already be enabled through the ef bit in the Configuration Setting Command. Use rfm12_set_rx_fifo_mode_enable() and apply that staged setting before reading the FIFO.

During FIFO access, the SPI clock frequency must not exceed one quarter of the crystal oscillator frequency. If the SPI clock duty cycle is not 50 percent, the shorter clock pulse must last at least two crystal oscillator periods.

Command Functions

rfm12_read_fifo()

RFM12_result_t rfm12_read_fifo(RFM12_t *dev, uint8_t *data)

Read one byte from the receiver FIFO immediately.

This function communicates with the radio through the configured SPI callback and returns the received FIFO byte through data.

Parameters:

• dev – RFM12 radio instance.

• data – Receives the byte read from the receiver FIFO.

Returns:

RFM12_OK on success, or an appropriate RFM12_result_t error.