Sansa e200 series FM tuner interface v0.2

by MrH 2006



Disclaimer
----------

I have the Euro model, which does not include a tuner, i.e. I haven't
tested this. I have 99.9% confidence on it though. If you find any
errors or omissions, let me know.



The tuner
---------

The FM tuner on Sansa e200 series is a Sanyo LV24020LP (U.S. models
only). At the time of writing this a proper register level datasheet
of it is available at:

http://www.semiconductor-sanyo.com/ds_e/ENA0070.pdf

Note that there also exists a shorter version of the datasheet (without
register descriptions) named 'ENA0070A.pdf' floating around in the web.
Be sure to get the real one.



Control interface
-----------------

The tuner is controlled via a 3-wire syncronous serial bus implemented
by bit-banging GPIO pins. It uses following pins:

name	port	pin
-----------------------------------------
NR_W	H	3  (0 = read, 1 = write)
CLOCK	H	4
DATA	H	5

The data is sent and received 8 bits at a time LSB first. When writing,
the data is driven on the bus after the falling edge of the clock and
sampled by the tuner on the rising edge. When reading the tuner drives
the data on the bus after the falling edge of the clock and the CPU
samples the data on the rising edge. See the datasheet for diagrams.



Examples
--------

Note that these examples are provided just to give an idea how to
drive the interface. Refer to the actual datasheet for real min/max
timings etc.


Init
----

clear bit 11 of 0x70000020 /* what does this do? */
wait 5 usec
set CLOCK high, as output and enable it
set DATA as input and enable it
set NR_W low, as output and enable it
wait 5 usec
done


Writing a bit
-------------

set CLOCK low
set the bit on DATA
wait 1 usec
set CLOCK high
wait 1 usec
done


Reading a bit
-------------

set CLOCK low
wait 1 usec
read the bit on DATA
set clock high
wait 1 usec
done


Writing a byte
--------------

write 8 bits LSB first
done


Reading a byte
--------------

read 8 bits LSB first
done


Writing a register
------------------

set NR_W high (write)
set DATA as output
wait 1 usec
write register value (byte)  /* really in this order ?? */
write register number (byte)
set DATA as input
set NR_W low (read)
wait 1 usec
done


Reading a register
------------------

set NR_W high (write)
set DATA as output
wait 1 usec
write register number (byte)
set DATA as input
set NR_W low (read)
wait 1 usec
read register value (byte)
done



Register descriptions
---------------------

See the datasheet.