Thread: FM Transmitter Other Half
View Single Post
Zeta is offline Zeta
2013-12-15 , 19:53
Posts: 339 | Thanked: 1,623 times | Joined on Oct 2013 @ France
#1
Hello,

For those interested by adding an FM transmitter in an other half, here is something that could help : http://talk.maemo.org/showpost.php?p...&postcount=140

Originally Posted by minimos View Post
Personally I'm not interested in a FM transmitter, so I'm probably not going to make one myself, but just today I was going through various electronics-related news and I arrived to the pages of 'FMBerry', a FM transmitter piloted with Raspberry PI: https://github.com/manawyrm/FMBerry
Looking at the details, it uses as FM transmitter from the Sony Ericsson MMR-70, an add-on that can be found on fleabay for about 1 EUR.
At its core it uses the Alps chip TSM 1-6, which is controlled via I2C: https://www.mikrocontroller.net/atta...0251/MMR70.pdf
The chip and its circuitery seems to be sufficiently small to be incorporated into a Jolla cover (if you find a way to get the audio signal).
It is small and damn cheap.

However it can be seen that the chip is controlled by I2C, but the input signals are taken from a jack stereo input. This means, it could only be used by a other half with a cable that connect it to the headphone connector...

Or drive a I2C Digital to analog chip to generate the two channels that are then sampled by the FM transmitter... Not sure if I2C would be the best for that : on at 400kHz bus without any overhead, the theoretical rate of 50 kbytes/s, so for a 8 bits stereo stream a frequency of 25kHz could theotically be reached, and Shannon says it allow to represent at max 12.5kHz signals. Real values would even be a bit lower, so not much quality to expect here... (to compare : CD quality is 16 bits with 48kHz sampling)

Too bad Jolla didn't expose more things to the other half than I2C and power.

If someone wants to work on this, this thread is for him !
 

The Following 10 Users Say Thank You to Zeta For This Useful Post: