Rotary Encoder question...

[silverD]

I did confirm the encoder pins connect to pins 41 and 42 on the chip and then I found this:


I haven't been able to get the encoder to work though...

[neildavis]

Thanks, that helps a lot! I had overlooked those pins, which are unlabeled in the schematic of the AC6901. You are right--they possibly could be used for a rotary encoder, if there was appropriate software to respond to the pulses. The pins could be probably be pulled up by the micro and debounced by the code. So the potential is there. But the fact that there is no connector provided is suspicious.

Maybe this interface will be supported in a future revision of the product, or maybe they had trouble implementing the design and gave up. It could also be an interface for some other protocol such as I2C or even analog, like the push buttons. No way to know without more information. I'll look at the pins with a scope when I get my board to see if there are any other clues.

Chrome will translate the text from the article that silverD posted: http://sxemy-podnial.net/aiyima-blue...der-s-zapisyu/. There are some comments about grounding that are worth reading if you intend to use this board.

[tomzarbo]

SilverD,

I know you were basically trying to get the rotary encoder to work, and probably haven't had a chance to play with the board yet; but I'm curious as to what your feelings are on it's general performance. Noise level, sound quality, etc. I haven't used it an awful lot yet but I did hook it up to PE's 320-606 amp board: https://www.parts-express.com/tda749...2x50w--320-606

And it was quiet on it's output when in use, or paused, something I can't say for some other preamp boards I've messed with. I'm in the midst of finishing up two Bantam table radios; I had planned on using a small video player version of a larger preamp faceplate unit I used in the last bantam table radio I posted awhile back... too noisy, though. Had to scratch that idea. Out of three of the smaller preamp boards I purchased, only one was noise-free, the other two were really noisy. This preamp board seems to be fairly quiet, though.

I really hope I'm not sending you guys on a wild goose chase with this thing. I really wanted it to have a nice, functioning interface for a good-old-fashioned volume knob, but like Neil said,

maybe

they tried to do it, and it just didn't work out... or it will be on a future upgrade.

At any rate, I think it's a decent little player with a real remote, and it's pretty small... and most importantly, it's very shallow depth-wise. I think a bit under an inch deep -- which helps with packaging in smaller radio sizes, which I have a few on the back burner.

Thanks for all the help figuring this out so far guys!

TomZ

[Millstonemike]

SilverD's schematic shows the encoder pins as 1-2-3 with 3 being ground. If they're laid out on the module that way - with ground at the end - this may have not been designed for a common rotary encoder. The encoders' common pin is in the center of the three contacts.

[silverD]

Yeah it is odd. The image of the board has the pins numbered so you can cross-reference the two. Same pin count on the chip, but different model number that Tom's. Looks like the board part number might be SSM-Q668. The board I have just says Q668 but in a different location.

[silverD]

Has your board come in Neil?

[tomzarbo]

I have a bunch of different encoders if I can be of any assistance... ham-fisted though I am... 3 kinds from Digikey and one kind from Aliexpress.
TomZ

[neildavis]

Has your board come in Neil?

yes--today.

I have a lot of rotary encoders--I've used them for a number of different projects. I've written my own assembly code and interrupt handlers and I've used the Ardiuno library for the mechanical rotary encoders, so I know what to expect. But I really doubt that those pads have anything to do with a rotary encoder. I'll take a look at the connector on a scope to get a feel for what it is doing, and report back.

But I also want to test the audio quality of the board as a preamp. If the audio quality is good, I might go ahead and buy the development tools, since it would be nice to be able to change the code. But all that will take me a while--got a lot of other projects lined up.

[neildavis]

I verified what Tom wrote about pin 2 of the volume encoder--it is a digital output that jumps between 0 and 3.3V at around a 1 second rate when audio is playing. It also pulses at a faster rate for some settings, and sometimes it is a steady "high". Pin 3 is an input--you can pull it up with a 10K resistor. This is *not* what you would expect for a rotary encoder, although it is consistent with the way the keypad is implemented.

I tried wiring up a potentiometer to these pins, using pin 3 as an input, and put a push button switch in series to simulate the behavior of the other keys. But nothing changed as a result of applying different voltages to that pin. I also looked through the code for references to PortB_11 and PortB_12, which is how those pins are defined in the code that I have for this chip. These pins are defined in the code but I didn't see any code that did anything interesting in the code--just the definitions and the pins show up again in some commented-out sections.

I'll try a few other things, but right now I would conclude that the "volume encoder interface" isn't implemented in the code. Given that Pin 1 is ground and that Pin 2 is an output, this connector clearly isn't for a standard rotary encoder. There is a technique for using a rotary encoder with one analog input, but it will take some time to test a circuit like that.

Next up is set up an A/B test to compare the sound going through the device versus bypassing the device. If there is no obvious degradation of the the sound going through the device, I'll keep playing with it.

[silverD]

Thanks for digging into this Neil. I tried an encoder and a pot and came to a similar conclusion. Keep us posted on the sound quality.

[tomzarbo]

Thank you Neil, for spending your time trying to figure this out. I had hopes for it... but I really don't have much of an understanding of the time and effort it takes to really dig into it. Sorry that I lead everyone on a wild goose chase.

As an excuse, I think that the product information laid out clearly suggested a volume adjusting device of some type. I really thought it was going to pan out.

But thanks everyone for the effort.
TomZ

[neildavis]

That board is pretty amazing for the $15 or so that it costs. It's certainly worth putting in the time to understand it better. It still might pan out as a great find. But even if we can't have it do everything we want, it's a very good bargain radio/Bluetooth/music player/preamp. You didn't lead anyone on a goose chase--you just pointed out a very promising product, and we are grateful for that.

As I said, if the audio quality is good enough I might buy the developer toolkit. That would allow a lot of customization. The specs for the JL chip are fairly good -- 92db SNR for both the DAC and ADC, but sometimes the specs are misleading. A/B testing will tell...

Update: I tried using different CODECs for the Bluetooth connection from my Android phone, but the phone only reported SBC, which is the default Bluetooth CODEC that isn't very good. I looked through the AC6901 code again for other CODECs like AptX and AAC and LDAC, but I only found AAC. That's the default for the iPhone, so maybe AAC is supported. I tried using my wife's iPhone but couldn't figure out how to see which CODEC is being used. Maybe the iPhone uses AAC, but I'm pretty sure Android phones are limited to SBC with this device. So the Bluetooth controls work great, but the audio quality isn't as good as it could be. *sigh*.

On the other hand, it has no trouble with FLAC or variable bit rate MP3's from the USB input. FLAC is a lossless encoding method, so the audio quality is good. It took a while (almost a minute) to read a 128M USB stick that was full (about 1200 files), but once it figured out the directory it seemed to work well.

[tomzarbo]

Looking at the rear of the board again, I'm wondering if there isn't another possible connection to tap into.

Here is another pic of the 'operating function keys' if that can be believed. Could any of these connections do anything volume wise?

I think you guys are pretty much past these 'labels' and connections and are looking at the chip itself to determine what's 'possible' but I just wanted to bring it up in case we overlooked it. Could just be another bad translation issue though. I'm kind of assuming it's a remote IR receiver and support for alternate face panel buttons or something. Just didn't know if it was another 'hook-up' option to consider.



Also, Neil/Nate/Mike or anyone looking into this, did anyone see any issues with the underside of the board (the side that faces the front) regarding soldering the three terminals that we soldered connections to.
I wasn't sure that the backside of the board was soldered up correctly without taking off the board and soldering one of those leads on the back side which may not be making good connection.

This post farther up shows what I'm saying: http://techtalk.parts-express.com/fo...06#post1427706

Just trying to avoid any 'poor connections' becoming a problem in figuring things out. I had different voltages once I soldered up the back side of the board.

Thanks Neil, I don't feel so bad if you guys don't think it's a waste. I like it's compact form factor, it's not deep and it will fit in a lot of places, plus it's pretty quiet too. I have my music collection ripped as 128k MP3's for the most part... I find the quality okay for car stereo playing and for these little players as "radios" but nothing really 'hi-fi' in any way. It's nice to see that it has the ability to play high quality files too.

I'm just literally amazed at how much these little players can do with the 1/4" by 1/4" chips that are the brains that make them think and work.

Anyway, thanks to all.

TomZ

P.S. I have three new 'untouched' boards to mess with if anyone has any ideas.

[Millstonemike]

Looking at the rear of the board again, I'm wondering if there isn't another possible connection to tap into.

Here is another pic of the 'operating function keys' if that can be believed. Could any of these connections do anything volume wise?

I think you guys are pretty much past these 'labels' and connections and are looking at the chip itself to determine what's 'possible' but I just wanted to bring it up in case we overlooked it. Could just be another bad translation issue though. I'm kind of assuming it's a remote IR receiver and support for alternate face panel buttons or something. Just didn't know if it was another 'hook-up' option to consider.



Also, Neil/Nate/Mike or anyone looking into this, did anyone see any issues with the underside of the board (the side that faces the front) regarding soldering the three terminals that we soldered connections to.
I wasn't sure that the backside of the board was soldered up correctly without taking off the board and soldering one of those leads on the back side which may not be making good connection.

This post farther up shows what I'm saying: http://techtalk.parts-express.com/fo...06#post1427706

Just trying to avoid any 'poor connections' becoming a problem in figuring things out. I had different voltages once I soldered up the back side of the board.

Thanks Neil, I don't feel so bad if you guys don't think it's a waste. I like it's compact form factor, it's not deep and it will fit in a lot of places, plus it's pretty quiet too. I have my music collection ripped as 128k MP3's for the most part... I find the quality okay for car stereo playing and for these little players as "radios" but nothing really 'hi-fi' in any way. It's nice to see that it has the ability to play high quality files too.

I'm just literally amazed at how much these little players can do with the 1/4" by 1/4" chips that are the brains that make them think and work.

Anyway, thanks to all.

TomZ

P.S. I have three new 'untouched' boards to mess with if anyone has any ideas.

"Nothing Ventured, nothing gained." - Benjamin Franklin

I can guess at that connector, J9, given the schematic and Neil's "education" on the key pad functionality (I didn't know the chip could read analog voltage levels).

It seems to be an interface for a remote module. There's Gnd and +3.3 V out. The "Key" input is for yet another unique push button signal into the chip. I have no idea what the S/W may do with that function. Lastly, there's a tie-in with the IR interface. That might feed the IR signal to the remote module. A lot of the potential functionality is a guess without knowing how the PCB is / was intended to be used in other products.

[neildavis]

I can guess at that connector, J9,...it seems to be an interface for a remote module.

Of course, and it's easy to figure out what voltages are needed on the "Key" pin to provide a remote version of the keypad. But the keyboard is clumsy, as in order to increase volume you need to hold the >> button until it changes function to Vol+. Not good. The IR pin would allow you to control the volume "directly", without the long hold But the IR pin is more difficult, as it uses a 32-bit PPM stream to encode the key value.

I used the IR_protocol_analyzer software available here to look at the stream. It looks like there is a 15-bit header followed by 8-bit data and then the same 8-bit data "inverted", at a bit rate of 900Hz. It shouldn't be too hard to create the same stream with an Arduino micro. I've actually got all of the key codes figured out, but it would take some time to test the code and hook up a rotary encoder. But I still need to do an A/B test to make sure the audio quality is good enough to make the programming effort worthwhile.