FM Transmitter Mod

Will do. Thanks for your help. I'll post updates on this thread.

Would another possibility be, building a GPIO board that would connect to the mod, and send out audio, the same way I did on the raspberry pi?

I'm more specifically referring to the PiFM Project on the raspberry pi.

David

Raspberry Pi Radio Transmitter: 4 Steps

The MDK does generate clock and PWM outputs, so it appears it would be feasible to use the MuC in the same manner that they used the Pi.  In this case the audio would be an analog signal out of the TFA still, correct?  You would probably need to flywire a new circuit on the Perforated board, since the Audio card doesn't provide easy access to extra GPIO.

If you run into issue configuring any MuC outputs, we're here to help.  As for how the user tunes the transmitter, than can be easily done with an Android app and pass the information to your Moto Mod using the Raw protocol.

There's an interesting comment that this isn't really a good way to do FM since you "splash" out over other channels.  I thought your FM transmitter was a separate chip, controlled by i2c like the TFA is.  Pretty interesting just modulating a GPIO signal; not sure if that is easier or harder than a transmitter IC.

Great documentation so far, really interesting to see this evolving!  But you confused me when you mentioned 2 knobs next to the speaker.

The MDK does generate clock and PWM outputs, so it appears it would be feasible to use the MuC in the same manner that they used the Pi.  In this case the audio would be an analog signal out of the TFA still, correct?  You would probably need to flywire a new circuit on the Perforated board, since the Audio card doesn't provide easy access to extra GPIO.

If you run into issue configuring any MuC outputs, we're here to help.  As for how the user tunes the transmitter, than can be easily done with an Android app and pass the information to your Moto Mod using the Raw protocol.

There's an interesting comment that this isn't really a good way to do FM since you "splash" out over other channels.  I thought your FM transmitter was a separate chip, controlled by i2c like the TFA is.  Pretty interesting just modulating a GPIO signal; not sure if that is easier or harder than a transmitter IC.

Great documentation so far, really interesting to see this evolving!  But you confused me when you mentioned 2 knobs next to the speaker.

So sorry for the confusion. The knobs are actually pins that push inward on the spk_out plates. If you have a spare Audio Personality card at home, take off all the screws, and lift the lid. You'll notice that the speaker is attached to the lid, and there are two little pins that press down on the spark plugs. Those are the "Knobs" I was talking about. What I was think about doing was using a Audio Amplifier, and a FM Transmitter both from adafruit.

I've posted links to both below. Does this look like something that would be feasible?

https://www.adafruit.com/product/1958

https://www.adafruit.com/product/987

The main components I will use on my perforated board.

David

Quick question. About interfacing with the FM Component. Is there a Way to get right out and left out of the moto mod? How would I interface with something Like this? The AdaFruit cpp code is open sourced for the component though.

I would like to update you on my current approach. After finding the necessary components that can be used for interface, I want to be able to use the I2S signals to output the audio. I don't see this being too hard after a few weeks of playing around with the elements. Using the test points on the perforated board, I can wire up a stereo decoder from the I2S and I2C signals available from the MuC. These can provide Rout and Lout, which when passed to the FM Transmitter, can allow for successful transmission through the use of the I2C circuits that are available.

[   MuC   ] ----> [   I2S Stereo Decoder.  ] ------> [   FM Transmitter.   ]

This is the specification for the decoder:

https://learn.adafruit.com/adafruit-i2s-stereo-decoder-uda1334a

This is the specification for the FM Transmitter:

https://learn.adafruit.com/adafruit-si4713-fm-radio-transmitter-with-rds-rdbs-support

Sorry for missing this update, I guess the TFA9890 is mono audio only, which the reason for the i2s stereo decoder.  Did you look to see if there was anything in the TFA family that might make your firmware development easier?  Otherwise, this device looks like it will work well you'll just need to port the driver over.

No more trying to bit bang the FM output?  I definitely think you'll be happier using the si4713, looks like the project is coming together nicely!

I mean, why re-invent the wheel, right?

Could this be something more easily done with an ADA Fruit Playground express. If so, is there a resource on how to set this up maybe?

At that point are you doing much more than handling power from the MDK to the adafruit?  You'll end up with 2 development environments on two different processors, but at the moment cost isn't really a factor.  How do you plan on splitting responsibilities between the Playground and the MuC?

Actually it won't be necessary. The FM Xmitter and the Stereo decoder I think are the two main components in this equation. I need to figure out how to get the correct data outputs to the Stereo Decoder as well as the FM Xmitter. I know the I2S outputs from the MuC to the Stereo Decoder and the I2C outputs to the FM Xmitter. I need to check on How these are going to work. It's just a matter of studying NuttX backwards and front and figuring out how to write the software properly. I also need to figure out how to write a small Android app that can call functions specified in AdaFruit's interface for the two components.

https://learn.adafruit.com/adafruit-i2s-stereo-decoder-uda1334a/arduino-wiring-test

https://learn.adafruit.com/adafruit-si4713-fm-radio-transmitter-with-rds-rdbs-support/test-and-usage

So maybe if you could give me a hint as to how to implement this. I have completed the Blinky app by the way. So I am not a NuttX virgin. I have implemented that project successfully.