16. Low Battery Detector and Microcontroller Clock Divider Command

Sets the low-battery detector threshold and microcontroller clock-output frequency.

Register Fields

Bits	Name	Meaning	API
7:5	d2:d0	Clock-output frequency	rfm12_set_clock_output_frequency()
4	Fixed	Must be 0	None
3:0	v3:v0	Low-battery threshold	rfm12_set_low_battery_threshold()

The setters listed in the register field table above directly configure fields in the Low Battery Detector and Microcontroller Clock Divider Command. The setters and reset function update staged configuration without communicating with the radio. Use rfm12_apply_to_radio() to write the staged settings.

The detector and clock output are enabled separately through rfm12_set_low_battery_detector_enable() and rfm12_set_clock_output_enable() in the Power Management Command. The hardware eb bit enables the detector, while dc disables the clock output; the clock-output enable API handles this inverted polarity.

Command Functions

rfm12_set_clock_output_frequency()

RFM12_result_t rfm12_set_clock_output_frequency(RFM12_t *dev, RFM12_clock_output_frequency_t frequency)

Stage the microcontroller clock-output frequency.

Selection	d2:d0	Clock-output frequency
RFM12_CLOCK_OUTPUT_1MHZ	000	1 MHz
RFM12_CLOCK_OUTPUT_1_25MHZ	001	1.25 MHz
RFM12_CLOCK_OUTPUT_1_66MHZ	010	1.66 MHz
RFM12_CLOCK_OUTPUT_2MHZ	011	2 MHz
RFM12_CLOCK_OUTPUT_2_5MHZ	100	2.5 MHz
RFM12_CLOCK_OUTPUT_3_33MHZ	101	3.33 MHz
RFM12_CLOCK_OUTPUT_5MHZ	110	5 MHz
RFM12_CLOCK_OUTPUT_10MHZ	111	10 MHz

This selects the clock division ratio. The CLK output-buffer drive current is configured separately by rfm12_set_pll_output_buffer_current().

Parameters:

• dev – RFM12 radio instance.

• frequency – Predefined clock-output frequency selection.

Returns:

RFM12_OK on success, or an appropriate RFM12_result_t error.

rfm12_set_low_battery_threshold()

RFM12_result_t rfm12_set_low_battery_threshold(RFM12_t *dev, RFM12_low_battery_threshold_t threshold)

Stage the low-battery detector threshold voltage.

Select a predefined threshold from RFM12_LOW_BATTERY_THRESHOLD_2_25V through RFM12_LOW_BATTERY_THRESHOLD_3_75V in 0.10 V increments. Pass the enum constant rather than a numeric voltage.

The threshold is V_LB = 2.25 V + V * 0.10 V, where V is the four-bit v3:v0 field. This setter does not enable the detector; use rfm12_set_low_battery_detector_enable() for that setting.

Parameters:

• dev – RFM12 radio instance.

• threshold – Predefined low-battery threshold selection.

Returns:

RFM12_OK on success, or an appropriate RFM12_result_t error.

rfm12_reset_low_battery_clock()

RFM12_result_t rfm12_reset_low_battery_clock(RFM12_t *dev)

Reset the staged low-battery threshold and clock-divider settings 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.