Si473x i2c/i2s radio for Rasperrby Pi

sipiradio.py

#!/usr/bin/python3
import quick2wire.i2c as i2c
import time
import RPi.GPIO as GPIO
import alsaaudio
import threading
import logging
import sys

#Work in progress library for Si473x for Raspberry Pi by Jonathan Thorpe <jt@jonthorpe.net>
#SiPiRadio
#
#Wiring:
# RPi                      Si473x Module
# i2s SDA                  i2c SDIO
# i2s SCL                  i2c SCLK
#
# GPIO 15                  RESET
# GPIO 4                   RCLK
#
# PCM_CLK                  DCLK
# PCM_FS                   DFS
# PCM_IN                   DOUT
#
# GPIO 4 must be set to clock mode at the appropriate rate.
# Can't find a way to do this in Python yet - use the command line:
#   gpio -g mode 4 clock
#   gpio -g clock 4 34406
#
# Before running this program, you need to load the my_loader.c kernel module from here:
# https://www.raspberrypi.org/forums/viewtopic.php?f=44&t=91237
# 
# Before compiling this module, ensure daifmt is set in clock and frame slave mode (Si47xx operates in slave only mode):
# .daifmt = SND_SOC_DAIFMT_I2S | SND_SOC_DAIFMT_NB_NF | SND_SOC_DAIFMT_CBS_CFS
#
#
# TODO (essentially implement more of the programmer's guide):
#   1. Support AM/SW/LW
#   2. Get Status information
#   3. FM RDS information
#   4. Make sure I'm using ALSA properly - seems a bit hacky
#
# Acknowledgments:
#    https://github.com/rickeywang/Si4737_i2c was useful for seeing how to program this device over i2c

logging.basicConfig(stream=sys.stderr, level=logging.DEBUG)

# ===========================================================================
# Si473x I2C / I2S Class
# ===========================================================================

class SiPiRadio():
  #GPIO pin for issuing the device reset
  GPIO_RESET=15

  #Si473x i2c address
  I2C_ADDRESS=0x63

  #The i2s Device as found from ALSA (my_loader.ko)
  AUDIO_IN_DEV="hw:CARD=sndrpisimplecar,DEV=0"

  #Default device to send audio out of
  AUDIO_OUT_DEV="default"

  #Audio sample rate
  AUDIO_SAMPLE_RATE=48000
  AUDIO_CHANNELS=2
  AUDIO_BITS_SAMPLE=16

  pcm_audio_in=None
  pcm_audio_out=None

  REFCLK_FREQ=34406
  REFCLK_PRESCALE=1

  #Constants
  SI4735_CMD_POWER_UP=0x01
  SI4735_CMD_GET_REV=0x10
  SI4735_CMD_POWER_DOWN=0x11
  SI4735_CMD_SET_PROPERTY=0x12
  SI4735_CMD_GET_PROPERTY=0x13
  SI4735_CMD_FM_TUNE_FREQ=0x20, 0x00
  SI4735_CMD_FM_TUNE_STATUS=0x22
  SI4735_CMD_GET_INT_STATUS=0x14

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

  #Statuses
  SI4735_STATUS_CTS=0x80
  SI4735_STATUS_ERR=0x40
  SI4735_STATUS_STCINT=0x01

  #Properties
  SI4735_PROP_REFCLK_FREQ=0x00, 0x02, 0x01
  SI4735_PROP_REFCLK_PRESCALE=0x00, 0x02, 0x02
  SI4735_PROP_DIGITAL_OUTPUT_SAMPLE_RATE=0x00, 0x01, 0x04
  SI4735_PROP_DIGITAL_OUTPUT_FORMAT=0x00, 0x01, 0x02
  SI4735_PROP_RX_VOLUME=0x40, 0x00

  #Flags
  SI4735_DIGITAL_I2S=0x01, 0x00

  SI4735_FLG_INTACK=0x01

  #Modes
  SI4735_MODE_LW=0
  SI4735_MODE_AM=1
  SI4735_MODE_SW=2
  SI4735_MODE_FM=3
  mode=SI4735_MODE_FM

  record_stop = threading.Event()
  record_thread = None

  def byteHigh(self, val):
    return val >> 8

  def byteLow(self, val):
    return val & 0xFF

  def sendCommand(self, cmd, *args):
    with i2c.I2CMaster() as bus:
      if (isinstance(cmd, int)):
        bytesToSend=(cmd,) + args
      else:
        bytesToSend=cmd + args

      logging.debug("Command: " + " ".join('0x%02x' % i for i in bytesToSend))
      bus.transaction(i2c.writing_bytes(self.I2C_ADDRESS, *bytesToSend))

  def getStatus(self):
    with i2c.I2CMaster() as bus:
        return bus.transaction(i2c.reading(self.I2C_ADDRESS, 1))[0][0]

  def ctsWait(self):
    status = 0
    while not status & self.SI4735_STATUS_CTS:
      status = self.getStatus()
      logging.debug("Returned status is: {0:#04x}".format(status))

  def intWait(self, interruptType):
    status = 0

    while not status & interruptType:
      self.sendCommand(self.SI4735_CMD_GET_INT_STATUS, 0x00)
      time.sleep(0.125)
      status = self.getStatus()
      if (not status & interruptType):
        logging.debug('Still waiting. Got status {0:#04x}'.format(status))

  def sendWait(self, cmd, *args):
    self.sendCommand(cmd, *args)
    self.ctsWait()

  def setProperty(self, property, *args):
    self.sendWait((self.SI4735_CMD_SET_PROPERTY,)+property+args)

  def setupCaptureDevice(self):
    logging.debug('Setting up capture device')
    self.pcm_audio_in = alsaaudio.PCM(alsaaudio.PCM_CAPTURE, alsaaudio.PCM_NORMAL, self.AUDIO_IN_DEV)
    self.pcm_audio_in.setchannels(self.AUDIO_CHANNELS)
    self.pcm_audio_in.setrate(self.AUDIO_SAMPLE_RATE)
    self.pcm_audio_in.setformat(alsaaudio.PCM_FORMAT_S16_LE)

  def setupPlaybackDevice(self):
    logging.debug('Setting up playback device')
    self.pcm_audio_out = alsaaudio.PCM(alsaaudio.PCM_PLAYBACK, alsaaudio.PCM_NONBLOCK)
    self.pcm_audio_out.setchannels(self.AUDIO_CHANNELS)
    self.pcm_audio_out.setrate(self.AUDIO_SAMPLE_RATE)
    self.pcm_audio_out.setformat(alsaaudio.PCM_FORMAT_S16_LE)
    logging.debug('Done setting up playback device')

  def captureAudio(self, arg, stop_event):
   self.pcm_audio_in.setperiodsize(160)

   while(not self.record_stop.is_set()):
      l, data = self.pcm_audio_in.read()
      if l:
        #logging.debug("Sending output audio...")
        self.pcm_audio_out.write(data)

  def powerUp(self):
    logging.debug('Powering up si473x')
    GPIO.output(self.GPIO_RESET, False)
    time.sleep(0.01)
    GPIO.output(self.GPIO_RESET, True)
    time.sleep(0.01)

    self.sendWait(self.SI4735_CMD_POWER_UP, 0x00, self.SI4735_OUT_BOTH)

    #Configure REFCLK
    self.setProperty(self.SI4735_PROP_REFCLK_FREQ,
                     self.byteHigh(self.REFCLK_FREQ),
                     self.byteLow(self.REFCLK_FREQ))

    self.setProperty(self.SI4735_PROP_REFCLK_PRESCALE,
                     self.byteHigh(self.REFCLK_PRESCALE),
                     self.byteLow(self.REFCLK_PRESCALE))

    self.record_thread.start()

    self.setProperty(self.SI4735_PROP_DIGITAL_OUTPUT_SAMPLE_RATE,
                     self.byteHigh(self.AUDIO_SAMPLE_RATE),
                     self.byteLow(self.AUDIO_SAMPLE_RATE))

    self.setProperty(self.SI4735_PROP_DIGITAL_OUTPUT_FORMAT, *self.SI4735_DIGITAL_I2S)

  def setFrequency(self, freq):
    if(self.mode == self.SI4735_MODE_FM):
      logging.debug('Setting frequency to {0} ({1:#04x} {2:#04x})'.format(freq, self.byteHigh(freq), self.byteLow(freq)))
      self.sendWait(self.SI4735_CMD_FM_TUNE_FREQ, self.byteHigh(freq), self.byteLow(freq), 0x00, 0x00)

    logging.debug('Frequency set, just waiting for tuning to complete')
    self.intWait(self.SI4735_STATUS_STCINT)

    if(self.mode == self.SI4735_MODE_FM):
      self.sendCommand(self.SI4735_CMD_FM_TUNE_STATUS, self.SI4735_FLG_INTACK)

  def setVolume(self, vol):
    logging.debug('Setting volume to {0:#04x}'.format(vol))
    self.setProperty(self.SI4735_PROP_RX_VOLUME, vol)

  def init(self):    
    self.setupCaptureDevice()
    self.setupPlaybackDevice()

  def __init__(self):
    self.record_thread = threading.Thread(target=self.captureAudio, args=(1, self.record_stop))

radio = SiPiRadio()
GPIO.setmode(GPIO.BOARD)
GPIO.setup(radio.GPIO_RESET, GPIO.OUT)

radio.init()
radio.powerUp()
radio.setVolume(0x63)
radio.setFrequency(10570)

logging.debug("Execution Complete")

print("q=quit")
cmd = ""
while True:
   cmd = input("Command: ")
   if(cmd=="q"):
      break
   
radio.record_stop.set()

GPIO.cleanup()

@iz2k, glad you find the code useful - unfortunately, I stopped maintaining it as the Si4735 have become hard to source after Silicon Labs discontinued this particular IC. May I ask what sort of project you're using this for?

Thanks for the hints regarding REFCLK.

I am working on my flip-clock project: https://github.com/iz2k/flip-clock

Amongst others, I have used a USB RTL-SDR dongle to tune FM radio, and I was trying to build a new hat for the Pi including two MAX98357A I2S audio DAC (Left + Right) for the audio output, and connect the output of the SI4735 to the I2S input of the Pi. I am testing this with evaluation boards, and for now I can pipe the tuned radio incoming from I2S input to analog output of the Pi. I am confident I will get it piped to the I2S output, and thus to the 3W audio DACs.

I have noticed that the SI4735 is not easy to find, but I already have the unit in my Eval Kit which should be enough for my device. But just in case, do you happen to know a similar alternative that is not discontinued?