ESP32 bluetooth transceiver - Page 1
Forum section: electronics / beginners

author: shybovycha
author_rank: Newbie
timestamp: January 31, 2022, 06:14:55 am
content: G'day!I have an issue with my car: it does not support music playback via bluetooth. And with modern one-port-only phones it is most uncomfortable - especially during long Australian drives. So I figured with ESP32 and a bit of luck & brains I can solve this issue.I got two I2S modules for Arduino (MAX98357) and connected them to ESP32-WROOM-32 on a breadboard and it worked with acceptable audio quality.Then I thought it would be a good idea to put it in a more compact form, so I soldered it onto a perfboard - looks ugly as hell and I probably burned one of the DAC modules due to shortcircuit, but it still works (to some extent).The next logical thing would be to put it on a PCB. I also thought I could use single 2-channel DAC IC instead of two, so I found PCM5101 - seems to fit my needs just fine.I've been working on this simple design for some time now (my first design in years - consider it first overall) and managed to pack everything on a ESP32-sized 4-layer PCB.4 layer board costs same as 2-layer one and it is quite convenient - to my best knowledge, having power planes as two internal layers also helps with resonance, signal interference and other nasty stuff.The decision to solder an entire ESP32 board on one side of the board might be not the wise one, but on one hand I am not sure it will work (still waiting for components to be delivered from China) and it is way cheaper and easier to have an entire board with programmer and all the circuitry than do it myself in these shortages times.The decision to use 0402 SMD packages for components and big bulky tantalum caps comes solely from what was available on AliExpress (I know, not the best place to pick the components, but again - shortages and prices in Australia make up the situation).Most of PCB design considerations are coming from my poor understanding of the topic. But given it is a 3.3V application on a 20x20mm PCB with ground and VCC planes running in between signal lines (for the most part - the PCM IC requires the split-power, as far as I understand, so few of those lines had to go on a signal plane, so I did my best to make those traces as wide as possible). I assume returning currents should not be the big issue. But the interference could - the bluetooth module and the audio amplifier are my biggest suspects.Just for fun, I have designed an even smaller version of this device in EasyEda, getting rid of an entire ESP32-WROOM-32 board and replacing it with just the MCU itself.Ended up packing everything in half the size PCB - 10x27mm. But I have even more concerns about such a packed design - I guess interference might play a significant role in this setup.Would be glad to hear others' thoughts on the above design!Cheers,Artem

author: thinkfat
author_rank: Unknown
timestamp: January 31, 2022, 07:19:50 am
content: Interesting project. What part do you want comments on, the tiny single PCB version? Because that one looks a bit unfinished to me. It seems like there's 90% of the magic sprinkle missing that is needed to make the ESP32 work

author: shybovycha
author_rank: Newbie
timestamp: January 31, 2022, 08:50:54 am
content: Oh, sorry for not clarifying - I am keen for the opinions on the bigger PCB design.The tiny PCB was merely an experiment of mine to see if it is possible to lay out an entire ESP32 circuitry on a smaller surface than that of a pre-made module.I have followed thepicoclick projecton that, consulting theESP32 hardware design guidelines- seems like except of RF LC circuit I got everything about right - not using anything but few GPIO pins, no DAC/ADC, no sensors - so I assumed I can skip on those components.Here's the schematic for the tiny board, just in case:Also just in case, I am attaching the big board project files (KiCad 6), since images might not be the best option here