Si4735.h

/* Arduino Si4735 (and family) Library
 * See the README file for author and licensing information. In case it's
 * missing from your distribution, use the one here as the authoritative
 * version: https://github.com/csdexter/Si4735/blob/master/README
 *
 * This library is for use with the SparkFun Si4735 Shield or Breakout Board.
 * See the example sketches to learn how to use the library in your code.
 *
 * This is the main include file for the library.
 *
 * #define SI4735_DEBUG to get serial console dumps of commands sent and
 * responses received from the chip.
 * #define SI4735_NOI2C or SI4735_NOSPI to exclude I2C or SPI code; please
 * note that selecting an operation mode that has been excluded will result
 * in undefined behaviour.
 */

#ifndef _SI4735_H_INCLUDED
#define _SI4735_H_INCLUDED

#if defined(ARDUINO) && ARDUINO >= 100
# include <Arduino.h>
#else
# include <WProgram.h>
#endif

//Assign the default radio pin numbers (shield version)
#define SI4735_PIN_POWER 8
#define SI4735_PIN_RESET 9
#define SI4735_PIN_GPO2 2

//List of possible interfaces for Si4735
#define SI4735_INTERFACE_SPI 0
#define SI4735_INTERFACE_I2C 1

//Assign the SPI pin numbers (shield version)
//SDIO, GPO1 and SCLK always connected to MOSI, MISO and SCK for SPI mode
//SDIO and SCLK always connected to SDA and SCL for I2C mode
//SEN should be hardwired HIGH or LOW for I2C mode
#define SI4735_PIN_SEN SS

//Constants for hardwired pins
//Chip is always powered, do not use PIN_POWER semantics
#define SI4735_PIN_POWER_HW 0xFF
//Chip interfaced via I2C, GPO2 left floating or tied LOW
//Define both HW and HWL constants to suit both semantics when typing
#define SI4735_PIN_GPO2_HW 0xFF
#define SI4735_PIN_GPO2_HWL 0xFF
//Chip interfaced via I2C, SEN always HIGH, device address 0xC6
#define SI4735_PIN_SEN_HWH 0xFF
//Chip interfaced via I2C, SEN always LOW, device address 0x22
#define SI4735_PIN_SEN_HWL 0xFE

//List of possible modes for the Si4735 Radio
#define SI4735_MODE_LW 0
#define SI4735_MODE_AM 1
#define SI4735_MODE_SW 2
#define SI4735_MODE_FM 3

//Define Si47xx Command codes
#define SI4735_CMD_POWER_UP 0x01
#define SI4735_CMD_GET_REV 0x10
#define SI4735_CMD_POWER_DOWN 0x11
#define SI4735_CMD_SET_PROPERTY 0x12
#define SI4735_CMD_GET_PROPERTY 0x13
#define SI4735_CMD_GET_INT_STATUS 0x14
#define SI4735_CMD_PATCH_ARGS 0x15
#define SI4735_CMD_PATCH_DATA 0x16
#define SI4735_CMD_FM_TUNE_FREQ 0x20
#define SI4735_CMD_FM_SEEK_START 0x21
#define SI4735_CMD_FM_TUNE_STATUS 0x22
#define SI4735_CMD_FM_RSQ_STATUS 0x23
#define SI4735_CMD_FM_RDS_STATUS 0x24
#define SI4735_CMD_FM_AGC_STATUS 0x27
#define SI4735_CMD_FM_AGC_OVERRIDE 0x28
#define SI4735_CMD_TX_TUNE_FREQ 0x30
#define SI4735_CMD_TX_TUNE_POWER 0x31
#define SI4735_CMD_TX_TUNE_MEASURE 0x32
#define SI4735_CMD_TX_TUNE_STATUS 0x33
#define SI4735_CMD_TX_ASQ_STATUS 0x34
#define SI4735_CMD_TX_RDS_BUF 0x35
#define SI4735_CMD_TX_RDS_PS 0x36
#define SI4735_CMD_AM_TUNE_FREQ 0x40
#define SI4735_CMD_AM_SEEK_START 0x41
#define SI4735_CMD_AM_TUNE_STATUS 0x42
#define SI4735_CMD_AM_RSQ_STATUS 0x43
#define SI4735_CMD_AM_AGC_STATUS 0x47
#define SI4735_CMD_AM_AGC_OVERRIDE 0x48
#define SI4735_CMD_WB_TUNE_FREQ 0x50
#define SI4735_CMD_WB_TUNE_STATUS 0x52
#define SI4735_CMD_WB_RSQ_STATUS 0x53
#define SI4735_CMD_WB_SAME_STATUS 0x54
#define SI4735_CMD_WB_ASQ_STATUS 0x55
#define SI4735_CMD_WB_AGC_STATUS 0x57
#define SI4735_CMD_WB_AGC_OVERRIDE 0x58
#define SI4735_CMD_AUX_ASRC_START 0x61
#define SI4735_CMD_AUX_ASQ_STATUS 0x65
#define SI4735_CMD_GPIO_CTL 0x80
#define SI4735_CMD_GPIO_SET 0x81

//Define Si4735 Command flags (bits fed to the chip)
#define SI4735_FLG_CTSIEN 0x80
//Renamed to GPO2IEN from GPO2OEN in datasheet to avoid conflict with real
//GPO2OEN below. Also makes more sense this way: GPO2IEN -> enable GPO2 as INT
//GPO2OEN -> enable GPO2 generically, as an output
#define SI4735_FLG_GPO2IEN 0x40
#define SI4735_FLG_PATCH 0x20
#define SI4735_FLG_XOSCEN 0x10
#define SI4735_FLG_FREEZE 0x02
#define SI4735_FLG_FAST 0x01
#define SI4735_FLG_SEEKUP 0x08
#define SI4735_FLG_WRAP 0x04
#define SI4735_FLG_CANCEL 0x02
#define SI4735_FLG_INTACK 0x01
#define SI4735_FLG_STATUSONLY 0x04
#define SI4735_FLG_MTFIFO 0x02
#define SI4735_FLG_GPO3OEN 0x08
#define SI4735_FLG_GPO2OEN 0x04
#define SI4735_FLG_GPO1OEN 0x02
#define SI4735_FLG_GPO3LEVEL 0x08
#define SI4735_FLG_GPO2LEVEL 0x04
#define SI4735_FLG_GPO1LEVEL 0x02
#define SI4735_FLG_BLETHA_0 0x00
#define SI4735_FLG_BLETHA_12 0x40
#define SI4735_FLG_BLETHA_35 0x80
#define SI4735_FLG_BLETHA_U (SI4735_FLG_BLETHA_12 | SI4735_FLG_BLETHA_35)
#define SI4735_FLG_BLETHB_0 SI4735_FLG_BLETHA_0
#define SI4735_FLG_BLETHB_12 0x10
#define SI4735_FLG_BLETHB_35 0x20
#define SI4735_FLG_BLETHB_U (SI4735_FLG_BLETHB_12 | SI4735_FLG_BLETHB_35)
#define SI4735_FLG_BLETHC_0 SI4735_FLG_BLETHA_0
#define SI4735_FLG_BLETHC_12 0x04
#define SI4735_FLG_BLETHC_35 0x08
#define SI4735_FLG_BLETHC_U (SI4735_FLG_BLETHC_12 | SI4735_FLG_BLETHC_35)
#define SI4735_FLG_BLETHD_0 SI4735_FLG_BLETHA_0
#define SI4735_FLG_BLETHD_12 0x01
#define SI4735_FLG_BLETHD_35 0x02
#define SI4735_FLG_BLETHD_U (SI4735_FLG_BLETHD_12 | SI4735_FLG_BLETHD_35)
#define SI4735_FLG_RDSEN 0x01
#define SI4735_FLG_DEEMPH_NONE 0x00
#define SI4735_FLG_DEEMPH_50 0x01
#define SI4735_FLG_DEEMPH_75 0x02
#define SI4735_FLG_RSQREP 0x08
#define SI4735_FLG_RDSREP 0x04
#define SI4735_FLG_STCREP 0x01
#define SI4735_FLG_ERRIEN 0x40
#define SI4735_FLG_RSQIEN 0x08
#define SI4735_FLG_RDSIEN 0x04
#define SI4735_FLG_STCIEN 0x01
#define SI4735_FLG_RDSNEWBLOCKB 0x20
#define SI4735_FLG_RDSNEWBLOCKA 0x10
#define SI4735_FLG_RDSSYNCFOUND 0x04
#define SI4735_FLG_RDSSYNCLOST 0x02
#define SI4735_FLG_RDSRECV 0x01
#define SI4735_FLG_GRPLOST 0x04
#define SI4735_FLG_RDSSYNC 0x01
#define SI4735_FLG_AMPLFLT 0x01
#define SI4735_FLG_AMCHFLT_6KHZ 0x00
#define SI4735_FLG_AMCHFLT_4KHZ 0x01
#define SI4735_FLG_AMCHFLT_3KHZ 0x02
#define SI4735_FLG_AMCHFLT_2KHZ 0x03
#define SI4735_FLG_AMCHFLT_1KHZ 0x04
#define SI4735_FLG_AMCHFLT_1KHZ8 0x05
#define SI4735_FLG_AMCHFLT_2KHZ5 0x06

//Define Si4735 Function modes
#define SI4735_FUNC_FM 0x00
#define SI4735_FUNC_AM 0x01
#define SI4735_FUNC_VER 0x0F

//Define Si4735 Output modes
#define SI4735_OUT_RDS 0x00 // RDS only
#define SI4735_OUT_ANALOG 0x05
#define SI4735_OUT_DIGITAL1 0x0B // DCLK, LOUT/DFS, ROUT/DIO
#define SI4735_OUT_DIGITAL2 0xB0 // DCLK, DFS, DIO
#define SI4735_OUT_BOTH (SI4735_OUT_ANALOG | SI4735_OUT_DIGITAL2)

//Define Si47xx Status flag masks (bits the chip fed us)
#define SI4735_STATUS_CTS 0x80
#define SI4735_STATUS_ERR 0x40
#define SI4735_STATUS_RSQINT 0x08
#define SI4735_STATUS_RDSINT 0x04
#define SI4735_STATUS_ASQINT 0x02
#define SI4735_STATUS_STCINT 0x01
#define SI4735_STATUS_BLTF 0x80
#define SI4735_STATUS_AFCRL 0x02
#define SI4735_STATUS_VALID 0x01
#define SI4735_STATUS_BLENDINT 0x80
#define SI4735_STATUS_MULTHINT 0x20
#define SI4735_STATUS_MULTLINT 0x10
#define SI4735_STATUS_SNRHINT 0x08
#define SI4735_STATUS_SNRLINT 0x04
#define SI4735_STATUS_RSSIHINT 0x02
#define SI4735_STATUS_RSSILINT 0x01
#define SI4735_STATUS_SMUTE 0x08
#define SI4735_STATUS_PILOT 0x80
#define SI4735_STATUS_OVERMOD 0x04
#define SI4735_STATUS_IALH 0x02
#define SI4735_STATUS_IALL 0x01

//Define Si47xx Property codes
#define SI4735_PROP_GPO_IEN word(0x0001)
#define SI4735_PROP_DIGITAL_INPUT_FORMAT 0x0101
#define SI4735_PROP_DIGITAL_OUTPUT_FORMAT 0x0102
#define SI4735_PROP_DIGITAL_INPUT_SAMPLE_RATE 0x0103
#define SI4735_PROP_DIGITAL_OUTPUT_SAMPLE_RATE 0x0104
#define SI4735_PROP_REFCLK_FREQ 0x0201
#define SI4735_PROP_REFCLK_PRESCALE 0x0202
#define SI4735_PROP_FM_DEEMPHASIS 0x1100
#define SI4735_PROP_FM_CHANNEL_FILTER 0x1102
#define SI4735_PROP_FM_BLEND_STEREO_THRESHOLD 0x1105
#define SI4735_PROP_FM_BLEND_MONO_THRESHOLD 0x1106
#define SI4735_PROP_FM_ANTENNA_INPUT 0x1107
#define SI4735_PROP_FM_MAX_TUNE_ERROR 0x1108
#define SI4735_PROP_FM_RSQ_INT_SOURCE 0x1200
#define SI4735_PROP_FM_RSQ_SNR_HI_THRESHOLD 0x1201
#define SI4735_PROP_FM_RSQ_SNR_LO_THRESHOLD 0x1202
#define SI4735_PROP_FM_RSQ_RSSI_HI_THRESHOLD 0x1203
#define SI4735_PROP_FM_RSQ_RSSI_LO_THRESHOLD 0x1204
#define SI4735_PROP_FM_RSQ_MULTIPATH_HI_THRESHOLD 0x1205
#define SI4735_PROP_FM_RSQ_MULTIPATH_LO_THRESHOLD 0x1206
#define SI4735_PROP_FM_RSQ_BLEND_THRESHOLD 0x1207
#define SI4735_PROP_FM_SOFT_MUTE_RATE 0x1300
#define SI4735_PROP_FM_SOFT_MUTE_SLOPE 0x1301
#define SI4735_PROP_FM_SOFT_MUTE_MAX_ATTENUATION 0x1302
#define SI4735_PROP_FM_SOFT_MUTE_SNR_THRESHOLD 0x1303
#define SI4735_PROP_FM_SOFT_MUTE_RELEASE_RATE 0x1304
#define SI4735_PROP_FM_SOFT_MUTE_ATTACK_RATE 0x1305
#define SI4735_PROP_FM_SEEK_BAND_BOTTOM 0x1400
#define SI4735_PROP_FM_SEEK_BAND_TOP 0x1401
#define SI4735_PROP_FM_SEEK_FREQ_SPACING 0x1402
#define SI4735_PROP_FM_SEEK_TUNE_SNR_THRESHOLD 0x1403
#define SI4735_PROP_FM_SEEK_TUNE_RSSI_THRESHOLD 0x1404
#define SI4735_PROP_FM_RDS_INT_SOURCE 0x1500
#define SI4735_PROP_FM_RDS_INT_FIFO_COUNT 0x1501
#define SI4735_PROP_FM_RDS_CONFIG 0x1502
#define SI4735_PROP_FM_RDS_CONFIDENCE 0x1503
#define SI4735_PROP_FM_AGC_ATTACK_RATE 0x1700
#define SI4735_PROP_FM_AGC_RELEASE_RATE 0x1701
#define SI4735_PROP_FM_BLEND_RSSI_STEREO_THRESHOLD 0x1800
#define SI4735_PROP_FM_BLEND_RSSI_MONO_THRESHOLD 0x1801
#define SI4735_PROP_FM_BLEND_RSSI_ATTACK_RATE 0x1802
#define SI4735_PROP_FM_BLEND_RSSI_RELEASE_RATE 0x1803
#define SI4735_PROP_FM_BLEND_SNR_STEREO_THRESHOLD 0x1804
#define SI4735_PROP_FM_BLEND_SNR_MONO_THRESHOLD 0x1805
#define SI4735_PROP_FM_BLEND_SNR_ATTACK_RATE 0x1806
#define SI4735_PROP_FM_BLEND_SNR_RELEASE_RATE 0x1807
#define SI4735_PROP_FM_BLEND_MULTIPATH_STEREO_THRESHOLD 0x1808
#define SI4735_PROP_FM_BLEND_MULTIPATH_MONO_THRESHOLD 0x1809
#define SI4735_PROP_FM_BLEND_MULTIPATH_ATTACK_RATE 0x180A
#define SI4735_PROP_FM_BLEND_MULTIPATH_RELEASE_RATE 0x180B
#define SI4735_PROP_FM_BLEND_MAX_STEREO_SEPARATION 0x180C
#define SI4735_PROP_FM_NB_DETECT_THRESHOLD 0x1900
#define SI4735_PROP_FM_NB_INTERVAL 0x1901
#define SI4735_PROP_FM_NB_RATE 0x1902
#define SI4735_PROP_FM_NB_IIR_FILTER 0x1903
#define SI4735_PROP_FM_NB_DELAY 0x1904
#define SI4735_PROP_FM_HICUT_SNR_HIGH_THRESHOLD 0x1A00
#define SI4735_PROP_FM_HICUT_SNR_LOW_THRESHOLD 0x1A01
#define SI4735_PROP_FM_HICUT_ATTACK_RATE 0x1A02
#define SI4735_PROP_FM_HICUT_RELEASE_RATE 0x1A03
#define SI4735_PROP_FM_HICUT_MULTIPATH_TRIGGER_THRESHOLD 0x1A04
#define SI4735_PROP_FM_HICUT_MULTIPATH_END_THRESHOLD 0x1A05
#define SI4735_PROP_FM_HICUT_CUTOFF_FREQUENCY 0x1A06
#define SI4735_PROP_TX_COMPONENT_ENABLE 0x2100
#define SI4735_PROP_TX_AUDIO_DEVIATION 0x2101
#define SI4735_PROP_TX_PILOT_DEVIATION 0x2102
#define SI4735_PROP_TX_RDS_DEVIATION 0x2103
#define SI4735_PROP_TX_LINE_INPUT_LEVEL 0x2104
#define SI4735_PROP_TX_LINE_INPUT_MUTE 0x2105
#define SI4735_PROP_TX_PREEMPHASIS 0x2106
#define SI4735_PROP_TX_PILOT_FREQUENCY 0x2107
#define SI4735_PROP_TX_ACOMP_ENABLE 0x2200
#define SI4735_PROP_TX_ACOMP_THRESHOLD 0x2201
#define SI4735_PROP_TX_ACOMP_ATTACK_TIME 0x2202
#define SI4735_PROP_TX_ACOMP_RELEASE_TIME 0x2203
#define SI4735_PROP_TX_ACOMP_GAIN 0x2204
#define SI4735_PROP_TX_LIMITER_RELEASE_TIME 0x2205
#define SI4735_PROP_TX_ASQ_INTERRUPT_SOURCE 0x2300
#define SI4735_PROP_TX_ASQ_LEVEL_LOW 0x2301
#define SI4735_PROP_TX_ASQ_DURATION_LOW 0x2302
#define SI4735_PROP_TX_ASQ_LEVEL_HIGH 0x2303
#define SI4735_PROP_TX_ASQ_DURATION_HIGH 0x2304
#define SI4735_PROP_TX_RDS_INTERRUPT_SOURCE 0x2C00
#define SI4735_PROP_TX_RDS_PI 0x2C01
#define SI4735_PROP_TX_RDS_PS_MIX 0x2C02
#define SI4735_PROP_TX_RDS_PS_MISC 0x2C03
#define SI4735_PROP_TX_RDS_PS_REPEAT_COUNT 0x2C04
#define SI4735_PROP_TX_RDS_PS_MESSAGE_COUNT 0x2C05
#define SI4735_PROP_TX_RDS_PS_AF 0x2C06
#define SI4735_PROP_TX_RDS_FIFO_SIZE 0x2C07
#define SI4735_PROP_AM_DEEMPHASIS 0x3100
#define SI4735_PROP_AM_CHANNEL_FILTER 0x3102
#define SI4735_PROP_AM_AUTOMATIC_VOLUME_CONTROL_MAX_GAIN 0x3103
#define SI4735_PROP_AM_MODE_AFC_SW_PULL_IN_RANGE 0x3104
#define SI4735_PROP_AM_MODE_AFC_SW_LOCK_IN_RANGE 0x3105
#define SI4735_PROP_AM_RSQ_INTERRUPTS 0x3200
#define SI4735_PROP_AM_RSQ_SNR_HIGH_THRESHOLD 0x3201
#define SI4735_PROP_AM_RSQ_SNR_LOW_THRESHOLD 0x3202
#define SI4735_PROP_AM_RSQ_RSSI_HIGH_THRESHOLD 0x3203
#define SI4735_PROP_AM_RSQ_RSSI_LOW_THRESHOLD 0x3204
#define SI4735_PROP_AM_SOFT_MUTE_RATE 0x3300
#define SI4735_PROP_AM_SOFT_MUTE_SLOPE 0x3301
#define SI4735_PROP_AM_SOFT_MUTE_MAX_ATTENUATION 0x3302
#define SI4735_PROP_AM_SOFT_MUTE_SNR_THRESHOLD 0x3303
#define SI4735_PROP_AM_SOFT_MUTE_RELEASE_RATE 0x3304
#define SI4735_PROP_AM_SOFT_MUTE_ATTACK_RATE 0x3305
#define SI4735_PROP_AM_SEEK_BAND_BOTTOM 0x3400
#define SI4735_PROP_AM_SEEK_BAND_TOP 0x3401
#define SI4735_PROP_AM_SEEK_FREQ_SPACING 0x3402
#define SI4735_PROP_AM_SEEK_TUNE_SNR_THRESHOLD 0x3403
#define SI4735_PROP_AM_SEEK_TUNE_RSSI_THRESHOLD 0x3404
#define SI4735_PROP_AM_AGC_ATTACK_RATE 0x3702
#define SI4735_PROP_AM_AGC_RELEASE_RATE 0x3703
#define SI4735_PROP_AM_FRONTEND_AGC_CONTROL 0x3705
#define SI4735_PROP_AM_NB_DETECT_THRESHOLD 0x3900
#define SI4735_PROP_AM_NB_INTERVAL 0x3901
#define SI4735_PROP_AM_NB_RATE 0x3902
#define SI4735_PROP_AM_NB_IIR_FILTER 0x3903
#define SI4735_PROP_AM_NB_DELAY 0x3904
#define SI4735_PROP_RX_VOLUME 0x4000
#define SI4735_PROP_RX_HARD_MUTE 0x4001
#define SI4735_PROP_WB_MAX_TUNE_ERROR 0x5108
#define SI4735_PROP_WB_RSQ_INT_SOURCE 0x5200
#define SI4735_PROP_WB_RSQ_SNR_HI_THRESHOLD 0x5201
#define SI4735_PROP_WB_RSQ_SNR_LO_THRESHOLD 0x5202
#define SI4735_PROP_WB_RSQ_RSSI_HI_THRESHOLD 0x5203
#define SI4735_PROP_WB_RSQ_RSSI_LO_THRESHOLD 0x5204
#define SI4735_PROP_WB_VALID_SNR_THRESHOLD 0x5403
#define SI4735_PROP_WB_VALID_RSSI_THRESHOLD 0x5404
#define SI4735_PROP_WB_SAME_INTERRUPT_SOURCE 0x5500
#define SI4735_PROP_WB_ASQ_INTERRUPT_SOURCE 0x5600
#define SI4735_PROP_AUX_ASQ_INTERRUPT_SOURCE 0x6600
#define SI4735_PROP_DEBUG_CONTROL 0xFF00

//This holds the current station reception metrics as given by the chip. See
//the Si4735 datasheet for a detailed explanation of each member.
typedef struct {
    byte STBLEND;
    bool PILOT;
    byte RSSI;
    byte SNR;
    byte MULT;
    signed char FREQOFF;
} Si4735_RX_Metrics;

class Si4735
{
    public:
        /*
        * Description:
        *   This the constructor. It assumes SparkFun Si4735 Shield + level
        *   shifter (or the diode fix, or 3.3V-native Arduino) semantics if
        *   called without parameters.
        *   If you're not using the Shield (e.g. using the Breakout Board) or
        *   have wired the Si4735 differently, then explicitly supply the
        *   constructor with the actual pin numbers.
        *   Use the hardwired pins constants above to tell the constructor you
        *   haven't used (and hardwired) some of the pins.
        * Parameters:
        *   interface - interface and protocol used to talk to the chip
        *   pin*      - pin numbers for connections to the Si4735, with
        *               defaults for the SparkFun Si4735 Shield already
        *               provided.
        */
        Si4735(byte interface = SI4735_INTERFACE_SPI,
               byte pinPower = SI4735_PIN_POWER,
               byte pinReset = SI4735_PIN_RESET,
               byte pinGPO2 = SI4735_PIN_GPO2, byte pinSEN = SI4735_PIN_SEN);

        /*
        * Description:
        *   This is the destructor, it shuts the Si4735 down
        */
        ~Si4735() { end(true); };

        /*
        * Description:
        *   Initializes the Si4735, powers up the radio in the desired mode
        *   and limits the bandwidth appropriately.
        *   This function must be called before any other radio command.
        *   The band limits are set as follows:
        *     LW - 152 to 279 kHz
        *     AM - 520 to 1710 kHz
        *     SW - 2.3 to 23 MHz
        *     FM - 87.5 to 107.9 MHz
        * Parameters:
        *   mode        - The desired radio mode, one of the SI4735_MODE_*
        *                 constants.
        *   xosc        - A 32768Hz external oscillator is present.
        *   slowshifter - A BOB-12009 is used for level shifting between an
        *                 Uno/Mega and the Si4735. Use a 3.3V I/O Arduino or
        *                 shift through a BOB-11771 to be able to go up to
        *                 1MHz by setting this to false.
        *                 NOTE: this is ignored for I2C mode which always uses
        *                 100kHz.
        *   interrupt   - Interrupt mode is to be used (as opposed to polling)
        *                 when waiting for the chip to perform an operation.
        */
        void begin(byte mode, bool xosc = true, bool slowshifter = true,
                   bool interrupt = false);

        /*
        * Description:
        *   Used to send a command and its arguments to the radio chip.
        * Parameters:
        *   command - the command byte, see datasheet and use one of the
                      SI4735_CMD_* constants
        *   arg1-7  - command arguments, see the Si4735 Programmers Guide.
        */
        void sendCommand(byte command, byte arg1 = 0, byte arg2 = 0,
                         byte arg3 = 0, byte arg4 = 0, byte arg5 = 0,
                         byte arg6 = 0, byte arg7 = 0);

        /*
        * Description:
        *   Acquires certain revision parameters from the Si4735 chip, returns
        *   the last two digits of the chip part number (e.g. 35 for Si4735).
        * Parameters:
        *   FW  - Firmware Version and it is a 2 character string
        *   CMP - Component Revision and it is a 2 character string
        *   REV - Chip Die Revision and it is a single character
        *   Set to NULL (or ignore) whichever parameter you don't care about.
        * Chips are usually referred in datasheets as "Si4735-$REV$FW", for
        * example "Si4735-C40" for the chip on the Sparkfun Shield.
        */
        byte getRevision(char* FW = NULL, char* CMP = NULL, char* REV = NULL,
                         word* patch = NULL);

        /*
        * Description:
        *   Used to to tune the radio to a desired frequency. The library uses
        *   the mode indicated via begin() to determine how to set the
        *   frequency.
        * Parameters:
        *   frequency - The frequency to tune to, in kHz (or in 10kHz if using
        *               FM mode).
        */
        void setFrequency(word frequency);

        /*
        * Description:
        *   Gets the frequency the chip is currently tuned to.
        * Parameters:
        *   valid - will be set to true if the chip currently detects a valid
        *           (as defined by current Seek/Tune criteria, see
        *           FM_SEEK_TUNE_* properties in the datasheet) signal on this
        *           frequency. Omit if you don't care.
        */
        word getFrequency(bool* valid = NULL);

        /*
        * Description:
        *   Commands the radio to seek up to the next valid channel.
        * Parameters:
        *   wrap - set to true to allow the seek to wrap around the current
        *          band.
        */
        void seekUp(bool wrap = true);

        /*
        * Description:
        *   Commands the radio to seek down to the next valid channel.
        * Parameters:
        *   wrap - set to true to allow the seek to wrap around the current
        *          band.
        */
        void seekDown(bool wrap = true);

        /*
        * Description:
        *   Adjust the threshold levels of the seek function.
        *   FM Ranges:
        *     SNR = [0-127] in dB, default = 3dB
        *     RSSI = [0-127] in dBuV, default = 20dBuV
        *   AM Ranges:
        *     SNR = [0-63] in dB, default = 5dB
        *     RSSI = [0-63] in dBuV, default = 19dBuV
        */
        void setSeekThresholds(byte SNR, byte RSSI);

        /*
        * Description:
        *   If in FM mode and the chip has received any RDS group, fetch it
        *   off the chip and fill word block[4] with it, returning true;
        *   otherwise return false without side-effects.
        *   As RDS has a [mandated by standard] constant transmission rate of
        *   11.4 groups per second, you should actively call this function (e.g.
        *   from loop()) so that you read most if not all of the error-corrected
        *   RDS groups received. For example:
        *   loop() {
        *     while(Si4735::readRDSGroup(data))
        *       RDSDecoder::decodeRDSGroup(data);
        *   }
        */
        bool readRDSGroup(word* block);

        /*
        * Description:
        *   Returns true if at least one RDS group has been received while
        *   tuned into the current station.
        */
        bool isRDSCapable(void) { return _haverds; };

        /*
        * Description:
        *   Retrieves the Received Signal Quality metrics using a
        *   Si4735_RX_Metrics struct.
        */
        void getRSQ(Si4735_RX_Metrics* RSQ);

        /*
        * Description:
        *   Disables debugging mode, fixes periodic click in audio. Only
        *   applicable to revision D60 and later devices. See AN332 for
        *   more details.
        */
        void disableChipDebug(void) {
            setProperty(SI4735_PROP_DEBUG_CONTROL, 0x0000);
        };

        /*
        * Description:
        *   Sets the volume. Valid values are [0-63].
        */
        void setVolume(byte value) {
            setProperty(SI4735_PROP_RX_VOLUME,
                        word(0x00, constrain(value, 0, 63)));
        };

        /*
        * Description:
        *   Gets the current volume.
        */
        byte getVolume(void) {
            return lowByte(getProperty(SI4735_PROP_RX_VOLUME));
        };

        /*
        * Description:
        *   Increase the volume by 1. If the maximum volume has been
        *   reached, no further increase will take place and returns false;
        *   otherwise true.
        */
        bool volumeUp(void);

        /*
        * Description:
        *   Decrease the volume by 1. If the minimum volume has been
        *   reached, no further decrease will take place and returns false;
        *   otherwise true.
        * Parameters:
        *   alsomute - mute the output when reaching minimum volume, in
        *               addition to returning false
        */
        bool volumeDown(bool alsomute = false);

        /*
        * Description:
        *   Mutes the audio output.
        */
        void mute(void) {
            setProperty(SI4735_PROP_RX_HARD_MUTE, word(0x00, 0x03));
        };

        /*
        * Description:
        *   Unmutes the audio output.
        * Parameters:
        *   minvol - set the volume to minimum value before unmuting if true,
        *            otherwise leave it untouched causing the chip to blast
        *            audio out at whatever the previous volume level was.
        */
        void unMute(bool minvol = false);

        /*
        * Description:
        *   Gets the current status (short read) of the radio. Learn more
        *   about the status byte in the Si4735 Datasheet.
        */
        byte getStatus(void);

        /*
        * Description:
        *   Gets the long response (long read) from the radio. Learn more
        *   about the long response in the Si4735 Datasheet.
        * Parameters:
        *   response - A byte[] at least 16 bytes long for the response from
        *              the radio to be stored in.
        */
        void getResponse(byte* response);

        /*
        * Description:
        *   Powers down the radio.
        * Parameters:
        *   hardoff - physically power down the chip if fed off a digital pin,
        *             otherwise just send SI4735_CMD_POWER_DOWN.
        */
        void end(bool hardoff = false);

        /*
        * Description:
        *   Sets deemphasis time constant (see SI4735_FLG_DEEMPH_*).
        */
        void setDeemphasis(byte deemph);

        /*
        * Description:
        *   Gets the current mode of the radio (see SI4735_MODE_*).
        */
        byte getMode(void) { return _mode; };

        /*
        * Description:
        *   Sets the Mode of the radio.
        * Parameters:
        *   mode      - the new mode of operation (see SI4735_MODE_*).
        *   powerdown - power cycle the chip first.
        *   xosc      - an external 32768Hz oscillator is present.
        *   interrupt - use interrupts (instead of polling) to wait on the chip.
        */
        void setMode(byte mode, bool powerdown = true,
                     bool xosc = true, bool interrupt = false);

        /*
        * Description:
        *   Sets a property value, see the SI4735_PROP_* constants and the
        *   Si4735 Datasheet for more information.
        */
        void setProperty(word property, word value);

        /*
        * Description:
        *   Gets a property value, see the SI4735_PROP_* constants and the
        *   Si4735 Datasheet for more information.
        * Returns:
        *   The current value of property.
        */
        word getProperty(word property);

    private:
        byte _pinPower, _pinReset, _pinGPO2, _pinSDIO, _pinGPO1, _pinSCLK;
        static byte _pinSEN;
        byte _mode, _response[16];
        static byte _i2caddr;
        bool _haverds, _interrupt, _seeking;
        static volatile byte _status;

        /*
        * Description:
        *   Enables RDS reception.
        */
        void enableRDS(void);

        /*
        * Description:
        *   Waits for completion of various operations.
        * Parameters:
        *   which - interrupt flag to wait for, see SI4735_STATUS_*
        */
        void waitForInterrupt(byte which);

        /*
        * Description:
        *   Performs actions common to all tuning modes.
        */
        void completeTune(void);

        /*
        * Description:
        *   Services interrupts from the Si4735.
        */
        static void interruptServiceRoutine(void);

        /*
        * Description:
        *   Requests the status (short read) of the last command from the chip.
        */
        static void updateStatus(void);

        /*
        * Description:
        *   Does the actual work of sending the command to the chip.
        */
        static void sendCommandInternal(byte command, byte arg1 = 0,
                                        byte arg2 = 0, byte arg3 = 0,
                                        byte arg4 = 0, byte arg5 = 0,
                                        byte arg6 = 0, byte arg7 = 0);
};

#endif