Testing ebay bluetooth audio modules

I found out some more about this module.

First no capacitators are needed at all on the headphone output, it will drive a HD201 to the pain level, and with no signal there is about .5 mA current in a short, so the diafragms of the headphones will be slightly biased, but that is OK.

Second, very nice is that this chip has a build in lipo charger. If you connect +5V to the pin marked Vcc, then it changes any lipo connected to Vbat with 103 mA (regulated) (measured, datasheet says 100 mA). The second LED than comes on permanently while charging.

So you can charge this from any USB, only needs a connector.

This is not documented in the usual online things, but I just tested that. It _is_ in the chip datasheet however. Traced the PCB tracks, and indeed pin 25 of the OVC3860 marked 'VPOW' goes to the board edge pin 9 marked VCC. See chip datasheet.

I will use this module to connect to USB:

It provides: connector, RS232 interface that works in Linux, and allows me to talk to the serial port of this module (seems 115200 Bd) (not tested yet).

There is no real need to do that to get it to work, but I think I can dump the on board EEPROM (2408) that way, and maybe send some AT commands or whatever, I already use that serial module in an other project, works great.

As far as buttons go to control it, you REALLY only need a real on-of switch in the battery, as it still sucks a lot of current when switched off by pressing teh ON button for a long time. Else you will find your battery empty when you want to use it. It goes into paring mode immediately when powered on.

Sound quality is excellent, noise I cannot hear! and with no coupling caps audio is down to DC, at least ... well bass is good.

I like your project although my need is a bit different. In the morning I may spend an 90 minutes in prep for work. I have an internet radio and listen to Science 360 or Imus or Old time radio programs. I feed the internet radio into an FM transmitter and then lug around a transistor radio to listen while I work. It interferes with my work keeping the radio where I can hear it. I wish I had an FM receiver headset that was like earbuds without the wires. This Bluetooth headset is the style I have in mind.

So now my mind wonders to the transmitter you link to for use with the headset above.

I foresee a problem with distance, especially if the Bluetooth transmitter is in the house and I'm outdoors 75 ft away.

Anyone see options I don't? Mikek

gs,

JPG

+headphones

452.html ?

-Lasse

They look nice, but they are bluetooth, so I still wonder about distance. Mikek

OH, I take that back I do see the mention of FM on the unit. I've never ordered from ALI, But I may just buy those. Thanks, Mikek

On a sunny day (Sun, 15 Feb 2015 09:12:55 -0600) it happened amdx wrote in :

The headphone should speak A2DP protocol, in all the commercial screams on that amazon web site I do not see it mentioned, could have overlooked it, get a datasheet and see if it is mentioned. I suppose it is OK, but it is LG youneverknow, I say that because of my Hombot LG autonomous vacuum cleaner :-)

As to the distance, 10 m.. I would not count on more, when going upstairs when right above that bluetooth transmitter I sometimes have to move to get signal.

On a sunny day (Sun, 15 Feb 2015 07:30:38 -0800 (PST)) it happened Lasse Langwadt Christensen wrote in :

Well, decoding? Quote, in Chinglish:

"The machine can be equipped with a computer USB port or charger native, the charging process, the machine LED power indicator light, while the battery symbol on the display pulsating, fully charged, LED power indicator is off and the monitor battery symbol displayed on the full grid. (When the machine is not a long time, remove the batteries or over a period of time to charge the battery.) "

??? :-)

...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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I love to cook with wine.     Sometimes I even put it in the food.

That looks fine, I'll need to ban 3yr olds because of the chocking hazard, not a bad policy anyway. :-) Mikek

I once had a pair of Sony's that were IR, so I had to stay in the same room, but they were very high quality audio. They finally died after ~10 years :-( ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

And your dilemma was, how can I get myself to just repair them and not redesign them? :-) BTW, were you happy with your compressor design awhile back?

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So, needed a box, this one looked just right with the ear symbol:

And it all fits!

The USB connector is only for charging, the left white LED then comes on, USB cable not plugged in here.

These big connectors are a bit more sturdy than the micro USB or nano USB or whatever the current trend is.

Should have used 2 small 3mm LEDs, but hey, must empty junkbox, I have many of these white ones.

So, altogether total cost maybe ?? 10$ (already had the lipo 1Ah though), uses about 60 mA, makes for > 10 hours continuous use.

PS I tried the serial com at 115200 Bd and can send AT commands, there is a big pdf online somewhere that list them (all?). Anyways, you can for example set volume or start and stop pairing via AT commands, and also list the RAM So that last thing I tried,

In Linux bash is all you need, but make sure you set the serial port to 115200 Bd, then do a cat /dev/ttyUSB0 > logfile.txt and in the other terminal run this script:

let address=0 let hex_address=0

while [ 1 ] do printf -v hex_address %x $address

# echo $hex_address

echo -e "AT#MX$hex_address\r" > /dev/ttyUSB0 echo -e "AT#MX$hex_address\r"

let address=address+1

if [ "$address" == "65536" ] then echo "Ready"

exit 0; fi

# delay loop to give teh thing a chance to reply, increase 8192 if you get error messages (to fast) let aa=0 while [ 1 ] do let aa=aa+1 if [ "$aa" == "8192" ] then break fi # sleep 1 done

done

---------- After that you need to do some editing of the result and remove all the 'MEM:' stuff, and 'OK' lines Then, as it replies in hex, you need to do whatever it is you want to do, say convert it to binary like I did, for example this way.

/* Donutted into the public domain Jan Panteltje 2015

*/ #include #include #include

#define READSIZE 1024

int verbose;

int readline(FILE *file, char *contents) { int c, i, j; int skip_lf_flag;

if(verbose) { fprintf (stderr, "readline(): arg file=%lu\n", (long)file); }

skip_lf_flag = 0; j = 0; for(i = 0; i < READSIZE - 1; i++) { //int fgetc(FILE *stream); c = fgetc(file); if(c == EOF) { fclose(file); contents[j] = 0;/* EOF marker */

return EOF; }

/* for now allow only the sequence '//''/n' (decimal 82 10) for end of line continuation */ if(skip_lf_flag && (c == '\n') ) { /* skip LF */ skip_lf_flag = 0;

continue; }

/* allow continuation on next line */ if(c == '\') // dec 92 { // skip_lf_flag = 1;

// continue; }

if(c == '\n') // dec 10 { contents[j] = 0;/* string termination */

if(verbose) { fprintf(stderr, "readline(): returning contents=%s\n", contents); }

return 1;/* end of line */ }

/* only allow the sequency 92 10, nothing in-between to indicate continuation on the next line */ skip_lf_flag = 0; contents[j] = c; j++; } /* mmm since we are here, the line must be quite long, possibly something is wrong. Since I do not always check for a return 0 in the use of this function, just to be safe, gona force a string termination. This prevents stack overflow, and variables getting overwritten.

*/ contents[j] = 0;/* force string termination */ /*fclose(file);*/

if(verbose) { fprintf(stderr, "readline(): line to long, returning 0 contents=%s\n", contents); }

return 0; } /* end function readline */

int main(int argc, char **argv) { int a, b, c, i; char temp[1024];

for(i = 0; i < 65536; i++) { readline(stdin, temp);

b = sscanf(temp, "%x %x", &a, &c);

fprintf(stderr, "%d %02x\n", i, a);

fprintf(stdout, "%c", a); }

exit(0); } /* end function main */

Anyays there is not much in it, some strings about heap problems, and I found online somebdoy who tried different disassemblers on it, and he thinks it looks 'most' like ARM code. However I only tried 64 kB, doing a 32 address space takes way too long. And I have no idea of the chip registers, seem to see some interrupt vectors at the start of the code, so lets leave it at simple AT commands that then for example can be send by a simple Microchip PIC after a second for the ebay module to initialize, and that is it. For now my headphones work great with this box without any programming.

There is a little 24C08 (1kB) EEPROM on board, I think it remembers the volume settings (16 levels including zero), but I only tested once, could be I still had some voltage on it.

15 maximum is the default, just right for the headphones.

Project closed for now.

Hi !

I'm working on a project that uses a similar bluetooth module. I'm trying to read the current volume stored in the module. I figured maybe I can use the command that reads in RAM, like you did. Do you have anymore info on this? Maybe I can dump the whole memory, then change the volume with the simple AT command and then dump the whole memory again. Comparing theses two dumps should give me a hint where the volume is stored, right?

Thanks for your help

Hello everyone,

I got one problem with this module. I connect it to my speaker so I use the power from the speaker, no battery. The power is connected to Vbat pin of the module. Problem is when there is no device connect to the module, it wi ll enter sleep mode and then you cannot connect to it again unless turning off/on again.

So I wonder if there is method to prevent it to sleep? Maybe connecting the power to Vcc pin can do?

On a sunny day (Mon, 15 Feb 2016 01:22:46 -0800 (PST)) it happened snipped-for-privacy@gmail.com wrote in :

What module?

Jan, You want to sweep these with Holm Impulse and get back to me? I'm curious how good the audio is. A simple electret is usually a good enough mic for sweeping.

Holm Impulse (free)

WM61A reference microphone.

Steve

On a sunny day (Mon, 15 Feb 2016 11:33:20 -0800 (PST)) it happened snipped-for-privacy@gmail.com wrote in :

What are you talking about?

I'd like you to sweep the frequency response and measure the noise floor, using Holm Impulse or similar software, and external microphone with a good flat response.

Thanks,

Steve

Signal trains don't need microphones, or loudspeakers, for that matter.

If there were a loudspeaker or microphone in the path, they would dominate most variables being measured.

RL