• Now available on Tindie

    andriy.malyshenko04/28/2022 at 22:15 0 comments

    To support my Crowd Supply launch I've decided to promote ESP8266 version of the board via Tindie store. This board is a baby version of ESP32 design, lacking some features and having much smaller power house. I consider it 'just enough' for smaller projects, like talking gadgets or sound boxes, left alone speechless visual projects that can start talking with this board.


    All funds received will go for ESP32 version development, which I hope will see the daylight, as long as the project pre-launch will receive enough subscriptions. Having that said I'd like to ask again everyone to subscribe to Crowd Supply campaign, I'm really keen to release it to backers and see the projects it can host.

  • Crowd Supply campaign is pre-launched

    andriy.malyshenko04/04/2022 at 17:50 0 comments

    Just wanted to mention that I'm starting preparations for Crowd Supply campaign. Actually some work already performed and pre-launch page is live now. Currently I'm collecting subscribers that would be the basis for price and volume calculations, and if there is an interest for the board in the first place.

    I'd appreciate if everyone interested in this board to see daylight would subscribe, mainly because only high enough volumes would allow to keep the price reasonably low.


  • New mini board and smart speaker projects

    andriy.malyshenko03/30/2022 at 14:08 0 comments

    I've decided to run funding campaign for this project with Crowd Supply. I did it before with another project of mine and it went well. This means among other things a huge to do list for me, including finalizing design (and feature list accordingly) and working on thorough testing and validation.

    Closing feature list is the most complicated for me, since it is always so tempting to add few more bells and whistles here and there. Good method in that case is implement something myself and check what is missing and what is not used along the way. Following that path I've came to conclusion that I need mini board - this designed to be placed inside all kind of smart speakers and therefore has no screen and generally take considerably less space.

    I introduce to you ESP Audio Development Board Mini


    And here they are together with full-size boards, both ESP8266 and ESP32 models

    Compared to their full-size counter parts they've lost SD card and IR connectors, but in terms of audio capabilities, they're equivalent.

    One question I got asked by CS team is what for I'd like to have ESP8266 model, and point is - it costs almost the same, but far less capable. I don't know it myself, it isn't rational, but I still prefer to do simpler projects with smaller MCU, perhaps I get some kind of satisfaction when MCU resources are used as much as possible.

    As I said above, best way to validate design is to implement something yourself, and for that purpose I've built 2 small speakers project

    The first one is a small, but extremely loud for it's size, alarm speaker. It started in life as a DIY bluetooth speaker, but given it's audio capabilities I've decided repurpose it.

    So the first step is to disassemble original speaker



    Then I'm placing inside ESP8266 Audio Dev mini board, connect both speakers to amp outputs and power switch to header

    Power comes from 18650 battery placed on the back side and secured using couple of screws
    Then it is secured inside using standoffs the way that USB port is accessible from the side to allow charging and flashing (although I'm using OTA updates for simple changes)

    I've secured a window on the top to allow indication using built-in addressable LED, and here is the end result

    And the second project would be more sophisticated speaker based on ESP32 version of the board and great cspot repo which implements Spotify speaker on ESP32 chip.

    To house this project I've bought Logitech iPod speaker (that what we've called smart before). It has no use in today's standards and anyway it is sold as broken and I couldn't care less if it was possible to fix it.



    First I need to disassemble it and I did a monkey job of it and broke a couple of parts on the way, but in the end it is showing it's internals


    It has Li-Ion battery inside that I will use and 2 speakers (2 passives also), which is also match.

    Here is the original PCB, it goes to spare parts box

    Connections that I've made are following
    - Both speakers are connected using stock wires
    - On/Off switch will be placed on the buttons panel, as well as addressable status LED
    - Stock battery connection
    - Charging port soldered directly to USB 5V line - i can charge it using built in power port (and play audio at the same time)

    Than PCB screwed in place using one of the stands left from original PCB
    Last touch - place power switch and status led on the buttons panel, it was broken before, so my connector trying to replace missing piece
    End result doesn't look much different from the original speaker, but now has Spotify capability


  • Revisiting MAX98357A DAC

    andriy.malyshenko02/18/2022 at 14:13 0 comments

    When I've tested MAX98357A module before in this project, I came to conclusion that it is only capable to produce moderate quality audio for non-demading projects. Funny enough I couldn't be more wrong about it.

    While performing audio tests with the development board shared in the previous post I got the same scores, quite disappointing audio quality with hearable distortions. Datashees was much more optimistic on the chip's performance, so I sit to play around with some components to see if I can make it play better. Since there are not so many components to play around with, I started poking around output filters.


    Originally I put output LC-filters similar to Adafruit's module as on the picture above. Not very happy with the result I revisited MAX98357 datasheet and found that it does not require any output filters apart from the speaker itself service as LR filter

    So out of curiosity I've removed the filters altogether and funny enough DAC started to produce clear audio! Below is waveform with no filters (taken from toy-oscilloscope, sorry again)

    1KHz 

    2KHz
    10 KHz

    20 Khz

    It doesn't look very promising just yet, but at least it works up to 20KHz with no issues. Much better than before.

    Next I've connected simple RC filter with 2Ohm (1Ohm per output) and 4.7uF cap in parallel to setup first order Low-pass filter set to filter out frequencies above 16KHz, which is reasonable margin for relatively cheap speakers I have. Here is the waveform behind filter

    1KHz

    2KHz
    10 KHz

    20 KHz
    Now it looks much better and I claim this result as acceptable.

    The only issue I have now is that having 2Ohms in parallel with 6 Ohms speaker push down efficiency quite a lot (although it is not dramatic when you hear the difference) and resistors warming up quite badly. If I decrease resistor value to 1 Ohm (.5 Ohm each output) output stage is losing stability.

    So in the end I'm going for no filter at all, just as datasheet says. I can't hear the difference really, and efficiency means more to me in the context of battery life.

  • New custom PCB - MAX98357 powered stereo amp

    andriy.malyshenko02/09/2022 at 21:31 0 comments

    Based in the investigation done in this project I've decided to build series of development boards with audio capable DAC, starting from the ones with built-in amp. Since I already have in mind a kind of project I'd like to implement (no spoilers) i also planned some advanced peripheral on the board to support those projects.

    To be fair I've done both ESP8266 and ESP32, since in my opinion they are both great chips and being similar on the paper, they are in a quite different league if it comes to power reserves, therefore they are not really competing. For smaller projects I prefer simplicity of ESP8266, for larger projects - spacier ESP32.

    I'm using them both quite regularly, so why not to have 2 development boards instead of one.

    With that said, here they are.

    ESP8266 closer look

    ESP32 closer look

    So commonly they have

    - Stereo DAC with built in amp (2x MAX98357)

    - Power circuit with backup Li-Ion battery (using built-in battery holder or external using battery socket)

    - Battery charging IC and battery overcurrent protection IC

    - Battery voltage measurement with built-in ADC

    - Boost converter to keep the music going when battery voltage is too low

    - TFT screen (with touch support on the ESP32)

    - USB-serial bridge for normal flashing and serial debugging, with auto-flashing circuit

    - IR reciever to support IR remotes

    - Micro SD-CARD socket

    Given the extra pins on the ESP32 is exclusively has

    - RGB led on the board and connector for the external RGB LED strip

    - PSRAM

    - Joystick OR rotary encoder

    - Few HW touch pads

    - JTAG header for real debugging

    Currently I'm testing all the peripherals and doing some small improvements. Also I've adopted cspot repo to play Spotify as a smart speaker, and looking into adding visual feedback to above project. I want to put it into the case, for that purpose I've bough broken smart speaker and planning to replace internals with my dev board. More details in the next post (hopefully).

  • Project update

    andriy.malyshenko09/10/2021 at 09:23 1 comment

    At one point I've decided to create ESP-32 based web-radio in the case of old classic radio. 

    This one I've bought for around 50 euros, it wasn't working obviously, and frankly  didn't bother to fix it. From one point I'm not a big fan of AM, from the other it has a very peculiar schematics, it runs from mains directly without input transformer of any kind. If you push the socket in the "right" direction all metal parts will be live, so decided I wouln't want to have that anywhere in the house near children playing with screwdrivers.

    Going back to the project. I've forked Ka-Radio32 repo, which is a ready to use wifi radio project. What I needed to do is to add HW definition of my board, and more importantly add TAS5805 amp support, since this is the amp I have on the board. 

    With that done it is relatively easy to fins some space within the box for new board and remote control receiver. Also I've connected power-on switch from the radio itself, and put IR receiver under the front panel

    And the final result is below.

  • TAS5805M I2S DAC prototype

    andriy.malyshenko06/06/2021 at 20:28 0 comments

    I've decided to take stakes a little higher and prepared bigger version of previous prototype. New one used Texas Instruments TAS5805M DAC, which is a big upgrade actually

    - It have high power stage, producing up to 23W per each of 2 channels (yeah!)

    - obviously it requires more than 5V over USB, so i had to redesign power circuitry completely.

    - it requires I2C additional to I2S to communicate and few GPIOs to report it's status.


    Because power stage took a lot of PCB space, screen went other side of the board for now. On the bright side, i could take a larger screen, since i have plenty of space now.

    So all together it is quite a different beast and I'm trying to find time to write firmware to get it started even. I get Ka-Radio32 firmware working on both prototypes and it works brilliantly on PCM5102 version. Currently working on TAS5805M addon to jump start the big thing.

  • New PCB to play with (PCM5102A)

    andriy.malyshenko11/09/2020 at 14:14 0 comments

    To play more with best DAC found so far i preapred and ordered custom PCB. This uncludes ESP32 module socket, power converter for PCM5102, and DAC itself. Just for fun also added 8 sensor buttons, IR reciever and OLEd screen. For now no specific plans, just made audio part produce sound and looking for specific project to drop in

    And yes, i switched to ESP32 now. Having experimented a little, i see that single core ESP-8266 is not capable to handle wifi and mp3 audio decoding on single core. One way to go around that is to use external mp3 decoder, another it to use more cores. Second option looks more fun to me.

    For now flashed great ESP32_MP3_Decoder to start with. It plays internet stream smoothly, and audio quality is great, as far as i can tell. 

    And last note. For this one i used 10uF ceramic caps instead of tantal ones. Normally they are  not recommended for audio applications due to piezoelectric effects, but as far as i can tell, they are just good enough. I can't tell a difference, that is all that matters to me

  • Testing TDA1543A and TDA1545A

    andriy.malyshenko07/15/2020 at 20:17 0 comments

    Next to test was 2 classic budget ICs: TDA1543A and TDA1545A. Unfortunately, despite the time spent i failed to make them work properly. I suspect that they could be fakes, since i got them from chinese platform for a price of € 1,6 per 5 pieces, giving € 0,30 a piece. I have no plans to buy them from trusted supplier, since then price leaven no senso of using them in low-budget projects.

    Data format: left justified, stereo output

    Ouput: high-impedance, biased, requires output driver

    Price: ~€0.30 per unit

    So lets call them replicas of TDA154X and see how output  looks like. I've connected both according to original's datasheet, input still the same: mono wav file generated by esp8266 module using ESP8266Audio library modified for LJ format, industry standard 44.1Khz sampling rate. 


    TDA1545A, no output filters, 2KHz

    TDA1545A, no output filters, 10KHz

    Input signal is visible, so i guess data format is OK. However waveform is so messed up, i can't be bothered to connect it to amp and speakers.

    TDA1543A, no output filters, any signal

    I failed to make it work really, it looks like input format is wrong, even it is ok for TDA1545, and they suppose to have same input format. So nothing I really could say about that. 

    I tried few different ICs, from same seller however, so makes not much sense to expect a difference. 

  • Tests of PT8211 IC

    andriy.malyshenko07/14/2020 at 22:16 0 comments

    Next to test is bare naked I2C DAC from unknown to me chinese manufacturer. It is advertized as (not really) direct replacement of TDA1311 DAC ond partially its successors TDA154X series. It requires output driver and i added one using 4558D opamp according to dtasheet application circuit

    Data format: left justified, stereo output

    Ouput: high-impedance, biased, requires output driver

    Price: ~€0.10-0.20 per unit

    Clearly it is here because the price, and it is not expected to have hifi performance, but rather support low-cost audio driver in projects.

    Here is the setup. 

    Only element added to above is output 1uF cap to filter out DC.

    Again, I only have toy oscilloscope, therefore results will be eye measured:)

    Test signal is mono wav file generated by esp8266 module using ESP8266Audio library modified for LJ format, industry standard 44.1Khz sampling rate. 

    1KHz on the output, after driver

    2KHz after driver

    10KHz on the output, after driver

    20KHz on the output, after driver

    As you can be seen, already at 10Khz distortions are huge, and 20Khz is a mess. However up till 20Khz there is no fading out of signal, and despite harmonic distortions i expect it to sound quite nice (for the price). As i said before, this is bad candidate for Hi-Fi sound, but very promisiong chip for less demanding audio applications. I keen to see it in action.