Saab mic

[Seth]

I don't think the comparable volume is an issue anymore, when the rn52 module has been turned up to max (in software). Adding an amp circuit would also most likely work, but makes more work for me ;)

[Da Bear]

I think we should handle mic bias independently of the rn52 like the HCB700 does. I base that on all I have read of different people having problem with rn52 and microphone. :)

As you can see in my schematic the audio out is pre-amplified through the LM4950.
Since the bluetooth chip in the HCB is mono input/output only one amplifier is needed. If this should be implemented in the saab module, two amplifiers are needed.

Also the HCB have adjustable volume so I think, depending on wich level you choose the amplifier gets more or less voltage  - obviously :P
Have not measured that yet and don't know how many steps you can raise the volume.
I'll check that later some day when I update my schematic.

So in my mind, we _could_ use separate mic bias (ie scrap rn52 bias control), and add two amplifiers to the rn52 audio outputs. The output from rn52 should be possible to control through the at-mega depending on choosen volume level on the IHU?
I know that the IHU sends some message on how high volume you have in 0-100% steps. At least my Tech2 can read the values. How/if it's sent over canbus I have no idea.

So...more work for you :D

Sorry if my english is not perfect, I can read it better than i can write it :P

[Da Bear]

Edit: Problem solved. Just remembered I have an HCB 700 already installed in the car. Doh!

Da Bear wrote

Also the HCB have adjustable volume so I think, depending on wich level you choose the amplifier gets more or less voltage  - obviously :P
Have not measured that yet and don't know how many steps you can raise the volume.
I'll check that later some day when I update my schematic.

I have stumbled on a problem I can't solve right now. I think I need to put a load (simulate a speaker or an external amplifier) on the pre-amp to measure volume. Without load I get 5.67v regardless volume level.
Any ideas?

[leva3000]

Hi! Any updates?

[Seth]

I haven't played with the mic circuit any, but last night I did find out how easy it is to read and change rn52 settings...easier than I previously had thought. So turning up the mic bias in software might work...will have to test, obviously.

On another note, I'm still waiting for the slow boat from china to deliver v3.3a pcbs for testing/trials, but I've already started v3.4 pcbs...just added a physical switch to manually force Command mode, and just renamed some nets for easier identification; nothing major.

[leva3000]

Good news! Will waiting for results of tests. It is very important to have ability to use mic.

[Ziq]

Yes, I am also eager to see some progress here and my knowledge in audio circuitry i zero..

Björn, are you still stuck with the same problem?

Seth, have you had any success with the RN52 mic bias?

I've been holding off building a more proper board since this was in the works but I guess I have to put in some effort myself as well, do not have the time right now though.

If you haven't seen any progress lately i guess I need to build a temporary board at least, my breadboard behaves funny at the moment and I think it might be due to bad connections (RN52 reboots when I talk to it to much etc..).

[Karlis]

As a status update: me and Seth did two sessions of "live" mic tests. The conclusion is that the mic setting SM needs to be adjusted on RN52. We were encountering some background noises during the calls. Almost as if there was a bad ground somewhere. I've taken out the mic from my car and made a test cable to connect the mic directly to BlueSaab, just to test out if there's some wiring "magic" that takes place. Stay tuned...

[Da Bear]

Ziq, pretty much yes. I have unfortunately not done any more research on this. Since I already have a 3rd party handsfree I have not prioritized it. I have tried to focus more on custom text to SID.

[homerisback]

Hi,
Did someone manage to use the MIC-IN 3.5 jack on the BlueSAAB ? I thought Sam (sbt) did but I can't find his post about it...
I would try to do it even with a third party electret MIC that I own.
Thanks in advance

[sbt]

homerisback wrote

Hi,
Did someone manage to use the MIC-IN 3.5 jack on the BlueSAAB ? I thought Sam (sbt) did but I can't find his post about it...

Sorry, no, not me. I did make reference to handsfree volumes levels elsewhere, but that was relating to getting the BlueSaab output levels to match the IHU and other sources like the handsfree bluetooth unit I've got hooked up to the TEL interface (at the top of this thread). Now I've tweaked the amp module multiplier, it's working really well.

As I understand it, to get this working you'd need a mic with pre-amp, and changes to the software to configure the handsfree profile in the RN52. Also, you have to have BlueSaab connected and the IHU source set to CDC before a call is made/received (whereas using the TEL interface, the IHU handles the switch, and it doesn't even have to be on). I assume the RN52 switches from playback to telephone if that profile is activated, but I don't have the hardware to try this.
 

[Seth]

I was in the process of testing some things to try and get the saab mic to work when I found out that my mic was dead. So I can't do anymore testing until I get a replacement mic.

the BlueSaab schematic is laid out per the rn52 data sheet, which is for an electret mic, not a mic with a preamp, like the saab mic (can be). Although, using pins 2-3 on saab mic is supposed to be Unamplified. Using 1-3 is amplified.

I did some mods to the BlueSaab pcb (basically removed all components regarding the mic circuit) to try and test the input but I don't know if anything worked since my mic is dead.

All that to say that mic input is still in work. Not saying it's not gonna work, but a change is needed somewhere in order to get it to work (if possible).

On Mon, Feb 27, 2017 at 18:29 sbt [via BlueSaab Forum] <[hidden email]> wrote:

homerisback wrote

Hi,
Did someone manage to use the MIC-IN 3.5 jack on the BlueSAAB ? I thought Sam (sbt) did but I can't find his post about it...

Sorry, no, not me. I did make reference to handsfree volumes levels elsewhere, but that was relating to getting the BlueSaab output levels to match the IHU and other sources like the handsfree bluetooth unit I've got hooked up to the TEL interface (at the top of this thread). Now I've tweaked the amp module multiplier, it's working really well.

As I understand it, to get this working you'd need a mic with pre-amp, and changes to the software to configure the handsfree profile in the RN52. Also, you have to have BlueSaab connected and the IHU source set to CDC before a call is made/received (whereas using the TEL interface, the IHU handles the switch, and it doesn't even have to be on). I assume the RN52 switches from playback to telephone if that profile is activated, but I don't have the hardware to try this.
 

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[Frederik]

I got to hear that several people changed their Saab microphone due to background noice and/or bad sound. They replaced the microphone with compatible Nokia microphones or other supported brands that worked with the phone kit.

[czabel]

Hello everyone!

I'm new to the project, so forgive me if I'm missing information somewhere, but I'm newly returned to the wonderful world of Saab. Just purchased a 2000 9-5 Aero, and I'm missing the Bluetooth from my previous car.

To the point: I'd love to help get the handsfree functionality in place, if it isn't already there. I didn't see any mention of it in the 6.1 release post, so I'm guessing development has stalled.

For those who know, what still needs to be done? I'm an acoustical engineer with an EE degree and access to lots of fun equipment. I plan to pull the microphone out of my 9-5 and start interrogating it, do we know anything about it?

Looking forward to getting started, and ordering parts for my own module!

[Karlis]

Hi,

Welcome to the party! Our problem with hands free mode is the struggle to get the built-in SAAB mic to “cooperate” with RN52 Bluetooth module. If you have any ideas on how to get that all to work, you are more than welcome to share your findings.

[czabel]

Great, okay. I've got the RN52 datasheet up now. For my reference, is the plan to run new wires from the microphone back to the module? I suppose it would have to be, we probably can't get the CAN network to transmit audio to the module, correct?

[Karlis]

Yes, the idea was to run a separate wire from the front of the car to BlueSaab module and use a 3.5mm jack for mic input. Sending microphone signal through CAN would not work. In case of BlueSaab (simulating CD Changer) it would not make sense fora CD Changer to have any kind of input, so that’s definitely not implemented in I-bus. In case of OnStar, AFAIK, there’s a signal, that enables telephone alongside microphone. But who sends what and where and who enables what and where is a mystery to me.

In other words - the idea is to keep it simple. A direct wire from the microphone in the front of the car to a 3.5mm jack on BlueSaab. v6.1 has some test points for mic-in functionality testing. Look for pins/switch next to RN52 module.

[czabel]

Good point on the input to the CD changer, that wouldn't make any kind of sense.

At this point I'm going to just play with the mic on a component level as I don't have a BlueSaab or even an RN52. Sounds like there may be some unusual bits stuck to the mic, so I'll learn what that's about and go from there.

Thanks Karlis!

[Karlis]

From the testing Seth and I did way back in the day, it looks like there's some combo of RN52 mic-in gain and SAAB microphone setting. SAAB microphone has three (?) pins which, according to WIS are "High, Low and GND". There are only two wires coming out of the mic. On Seth's 9-3 these wires were connected to Low and GND. On my 9-5 they were connected to High and GND. We were playing around with SAAB microphone being connected directly to RN52 and were experimenting with RN52 mic-in gain settings, but all we got out was a "metallic" or "chirping" sound. So - no good. Maybe you'll be more lucky.  

[czabel]

Alright, made some progress tonight.

I've got the mic on the bench, running through one of our electret mic preamps (see schematic below)


My mic measures as follows:
Pins 1 & 3 = 6.5kOhm (High Impedance)
Pins 2 & 3 = 1.1kOhm (Low Impedance)

When using the low impedance configuration I can barely get a signal out. It's there, but almost in the noise. I'll keep playing with it, but the high impedance pins are where I had the best luck. I've uploaded the .WAV file I recorded out of the mic, seems to enjoy working from +4.5VDC on up (I stopped at 5.1V). The output amplitude doesn't change noticeably beyond 4.8V. As you can hear, it barely works at 4.4V, but after that is pretty clear. SaabMic_HighImp_VoltageTesting_01.wav

By closely examining the waveform, you can see that the amplitude of the background noise (equipment fan hum) does increase with voltage, but I would be inclined to run as low a bias voltage as possible, not knowing what the microphone module really wants.

Anyway, next step for me is to send Microchip an email asking for a dev board sample. They have a few methods of connecting a microphone on the board and I'd like to try them and mess around with their Mic_Bias line. Their datasheet leaves a lot to be desired... Sure, I get 1.5dB steps, but dB relative to what? 1V? Who knows.

Or, if they don't want to send me a sample, I'll just buy the stuff for a full BlueSaab and mess with it that way. Is it possible to interact with the RN52 directly when using the full BlueSaab? I see the UART headers, I'm guessing there's something I'll need to use to convert to USB?