11. TX Configuration Control Command¶

Configures FSK modulation polarity, frequency deviation, and transmitter output power.

Register Fields¶

Bits	Name	Meaning	API
8	`mp`	FSK modulation polarity	`rfm12_set_tx_fsk_polarity()`
7:4	`m3:m0`	FSK frequency deviation	`rfm12_set_tx_fsk_deviation()`
3	Fixed	Must be `0`	None
2:0	`p2:p0`	Output-power attenuation	`rfm12_set_tx_power()`

The setters listed in the register field table above directly configure fields in the TX Configuration Control Command. The setters and reset function update staged configuration without communicating with the radio. Use rfm12_apply_to_radio() to write the staged settings.

Command Functions¶

rfm12_set_tx_fsk_polarity()¶

RFM12_result_t rfm12_set_tx_fsk_polarity(RFM12_t *dev, RFM12_tx_fsk_polarity_t polarity)¶

Stage the FSK modulation polarity.

Select RFM12_TX_FSK_POLARITY_NORMAL for mp = 0: logic 0 produces the higher frequency and logic 1 produces the lower frequency. Select RFM12_TX_FSK_POLARITY_INVERTED for mp = 1: logic 0 produces the lower frequency and logic 1 produces the higher frequency.

The datasheet defines the output frequency as f_out = f0 + (-1)^SIGN * (M + 1) * 15 kHz, where SIGN = mp XOR FSK, FSK is the transmitted data bit, M is the encoded deviation field, and f0 is the carrier center frequency.

Parameters:

dev – RFM12 radio instance.
polarity – FSK modulation polarity selection.

Returns:

RFM12_OK on success, or an appropriate RFM12_result_t error.

rfm12_set_tx_fsk_deviation()¶

RFM12_result_t rfm12_set_tx_fsk_deviation(RFM12_t *dev, RFM12_tx_fsk_deviation_t deviation)¶

Stage the FSK frequency deviation from the carrier center frequency.

Select a predefined deviation from RFM12_TX_FSK_DEVIATION_15KHZ through RFM12_TX_FSK_DEVIATION_240KHZ in 15 kHz increments. Pass the enum constant rather than a numeric frequency.

The deviation magnitude is (M + 1) * 15 kHz, where M is the four-bit m3:m0 field. The two FSK frequencies lie this distance above and below the center frequency, so their separation is twice the selected deviation.

Parameters:

dev – RFM12 radio instance.
deviation – Predefined FSK frequency-deviation selection.

Returns:

RFM12_OK on success, or an appropriate RFM12_result_t error.

rfm12_set_tx_power()¶

RFM12_result_t rfm12_set_tx_power(RFM12_t *dev, RFM12_tx_power_t power)¶

Stage the transmitter output-power selection.

Selection	`p2:p0`	Relative output power
`RFM12_TX_POWER_0DB`	`000`	0 dB (maximum output)
`RFM12_TX_POWER_MINUS_2_5DB`	`001`	-2.5 dB
`RFM12_TX_POWER_MINUS_5DB`	`010`	-5 dB
`RFM12_TX_POWER_MINUS_7_5DB`	`011`	-7.5 dB
`RFM12_TX_POWER_MINUS_10DB`	`100`	-10 dB
`RFM12_TX_POWER_MINUS_12_5DB`	`101`	-12.5 dB
`RFM12_TX_POWER_MINUS_15DB`	`110`	-15 dB
`RFM12_TX_POWER_MINUS_17_5DB`	`111`	-17.5 dB

Select attenuation from maximum output in 2.5 dB increments, from 0 dB through 17.5 dB, using the enum constants above.

These values are relative to maximum available output power, not absolute power in dBm. Maximum available power depends on antenna impedance.

Parameters:

dev – RFM12 radio instance.
power – Transmitter output-power selection.

Returns:

RFM12_OK on success, or an appropriate RFM12_result_t error.

rfm12_reset_tx_configuration()¶

RFM12_result_t rfm12_reset_tx_configuration(RFM12_t *dev)¶

Reset the staged TX Configuration Control Command values to their defaults.

This function does not communicate with the radio. The changed settings are written to the radio by rfm12_apply_to_radio().

Parameters:

dev – RFM12 radio instance.

Returns:

RFM12_OK on success, or an appropriate RFM12_result_t error.