The interface between the MCU (micro controller unit) and the radio transceiver consists of the SPI interface (MISO, MOSI, SCLK, /SEL), digital control pins (/RST, SLP_TR and optional TST), the interrupt pin (IRQ) and the clock output pin (CLKM).
+-------+ +-------+
| | | |
| |<--MISO----| |
| |---MOSI--->| A |
| |---SCLK--->| T |
| MCU |---/SEL--->| 8 |
| | | 6 |
| |---/RST--->| R |
| |---SLP_TR->| F |
| | | 2 |
| |<--IRQ-----| 3 |
| |<--CLKM----| 0 |
| | | |
| |---(TST)-->| |
+-------+ +-------+
SPI stands for Serial Peripheral Interface and is a synchronous bidirectional serial data bus. The MCU has to be configured as SPI master in order to control the radio transceiver with the following primitives:
The low active control pin TRX_PIN_RST is used to reset the radio transceiver and has to be configured as an output pin of the MCU (see trx_pinset_reset).
- If TRX_PIN_RST = LOW, the radio transceiver is hold in reset
- If TRX_PIN_RST = HIGH, the radio transceiver is released from reset.
During normal operation, this pin is set to HIGH.
The function of the high active control pin TRX_PIN_SLP_TR is state dependent and it has to be configured as an output pin of the MCU (see trx_pinset_slptr).
- If TRX_PIN_SLP_TR = LOW, the radio transceiver is not influenced.
- If TRX_PIN_SLP_TR = HIGH, the following effects occur:
- in state TRX_OFF : the radio transceiver is set into the SLEEP state.
- in state PLL_ON : the sending of a frame is started (rising edge).
- in state TX_ARET_ON : a TX_ARET transaction is started (rising edge).
- in state RX_ON, RX_AACK_ON : forcing the radio transceiver into the corresponding *_NOCLK state, which means that no clock signal at the CLKM pin is delivered.
The TRX_PIN_IRQ pin changes from LOW to HIGH, if an asynchronous radio transceiver event occurs. It is an input (interrupt) pin of the MCU, which stays at HIGH level, until the interrupt cause is determined by reading the register RG_IRQ_STATUS.
The TRX_PIN_CLKM pin can provide a clock signal, which is derived from the radio transceiver clock. This signal can be used as clock source for a timer or as main clock for the MCU.
The high active control pin TRX_PIN_TST is used to enable or disable the continous transmission test mode of the radio transceiver. It can optionally be an output pin of the MCU (see trx_pinset_tst).
- If TRX_PIN_TST = LOW : the radio transceiver is in normal operating mode.
- If TRX_PIN_TST = HIGH : activate the continous transmission test mode.
- Note:
- For regular operation of the radio transceiver, it has to be ensured, that the pin TRX_PIN_TST is wired to ground or is fed with logical low level (TRX_PIN_TST = LOW). It is not necesarry to control this pin via the MCU, it can also be operated manually.
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