maemo.org - Talk - FM Transmitter Other Half

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- - FM Transmitter Other Half (https://talk.maemo.org/showthread.php?t=92037)

FM Transmitter Other Half

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

Quote:

Originally Posted by minimos (Post 1396839)

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 !

Rainsing Hand for Interest - FM Transmitter Thread

An FM Transmitter would really rock my commute to work. meanwhile I own an external FM transmitter. However, I wouldn't mind at all to use it for its USB loading port only.

icke

Re: FM Transmitter Other Half

One of the i2c buses in n900 (and I presume in N9/50 too) runs on 2200 KHz, maybe TOH bus can be programmed for such or higher speed. Wild guess only

Quote:

Originally Posted by freemangordon (Post 1396937)

One of the i2c buses in n900 (and I presume in N9/50 too) runs on 2200 KHz, maybe TOH bus can be programmed for such or higher speed. Wild guess only

@freemangordon will you use Jolla device? We all need you for kernel power!

Re: FM Transmitter Other Half

There's also the possibility to use some kind of audio compression , though it makes things both on the phone side and the other half more complicated.

There's been just the teensy 3.1 released, a tiny board with a 72mhz cortex m4 muC, 64k of ram + 256k flash, has dsp extensions, two i2c busses, spi, can,usb, some adcs and one 12 bit dac, Arduino-compatibility, and below 20 euro. Bit of an overkill just for an fm toh maybe, but could be a nice base for many projects:

www.pjrc.com/teensy/teensy31.html

Re: FM Transmitter Other Half

Quote:

Originally Posted by TMavica (Post 1396959)

@freemangordon will you use Jolla device? We all need you for kernel power!

Not interested as of now. Maybe will rethink if and when Jolla produces a device with HW KBD and FMTX :) . Till then I'll stick to N/eo900.

Re: FM Transmitter Other Half

Is there any news about this issue?