GuruBlog

Today I started working on the radio part of the raspberry pi radio. I hooked up an AR1010 based breakout board from sparkfun to the i2c ports of the raspberry pi and wrote a short python program to initialize the chip and tune it to a radio station.

It took me a while to figure out how to access the chip and after searching through tons of tutorials example-code and a really really really extremely bad datasheet I finally managed to get my code running.

The main reason why it didn´t work in the beginning was that I didn´t recognize that the smbus library sends long values in LSB,MSB order while the AR1010 wants them in MSB,LSB order :-/. Who would have thought that the littleendian/bigendian thing still exists in 2013

This is the code I use to initalize the radio after booting the pi

import smbus
import time
bus = smbus.SMBus(1)

adr = 0x10

init = [ 0xFFFB, 0x5B15, 0xD0B9, 0xA010, 0x0780, 0x28AB, 0x6400, 0x1EE7,
0x7141, 0x007D, 0x82C6, 0x4E55, 0x970C, 0xB845, 0xFC2D, 0x8097, 0x04A1,
0xDF6A ]

def swap( a ):
        return (a & 0xFF) << 0x8 | (a >> 0x8)

def write( chan, d ):
        bus.write_word_data( adr, chan, swap(d))

def read( chan ):
        tmp = bus.read_word_data( adr, chan )
        return swap( tmp )

def setbit( chan, bit ):
        tmp = read( chan )
        write( chan, tmp | 1 << bit )

def clearbit( chan, bit ):
        tmp = read( chan )
        write( chan, tmp & ~(1 << bit ))


 for i in range( 1,18 ):
        print i
        write( i, init[i] )
 write( 0, init[0] )

 print "getstatus"
 tmp = 0
 while ( tmp == 0 ):
        tmp = read( 0x13 ) & 0x20

and here is the code that tunes the radio to a frequency (103.8 in this case)

import smbus
import time
bus = smbus.SMBus(1)

adr = 0x10

def swap( a ):
        return (a & 0xFF) << 0x8 | (a >> 0x8)

def write( chan, d ):
        bus.write_word_data( adr, chan, swap(d))

def read( chan ):
        tmp = bus.read_word_data( adr, chan )
        return swap( tmp )

def setbit( chan, bit ):
        tmp = read( chan )
        write( chan, tmp | 1 << bit )

def clearbit( chan, bit ):
        tmp = read( chan )
        write( chan, tmp & ~(1 << bit ))


clearbit( 1, 1)
clearbit( 1, 2)

time.sleep(1)

f = 1038
clearbit( 2, 9 )
setbit(1,1)
print "freq"
tmp = read( 2 )
print hex(tmp)
tmp = tmp & 0xFE00
tmp = tmp | ( f - 690 )
print hex(tmp)
write( 2, tmp )
print "tuneon"

setbit( 2, 9 )
print "getstatus"
tmp = 0
while ( tmp == 0 ):
        tmp = read( 0x13 ) & 0x20

print bin(tmp)
clearbit(1,1)

Please note that this code is not considered production ready. I will try to access more advanced features of the radio module tomorrow and will publish the final radio part code later