[0:00] For the walkie talkie project, I made a custom PCB to hold the ESP32 dev board, the I2S amplifier and the I2S microphone.
[0:08] I also added a power filter for the microphone
[0:11] to help eliminate the noise we were getting when transmitting over WiFi.
[0:15] The board works really well, but there are a few things that need improving.
[0:19] The first slightly annoying omission that I made
[0:22] is that I didn’t expose any of the spare GPIO pins.
[0:25] This makes the PCB great if you only want to do an audio project
[0:29] but not very good if you’ve got other peripherals you want to connect.
[0:32] I’ve worked around this partially by using these very long headers, but it’s not ideal.
[0:37] The second thing I want to fix is that I’ve used pin 26
[0:41] this is one of the only two pins on the ESP32 that can be used for Digital to Analogue Conversion
[0:46] so I’d like to free it up for other projects
[0:49] The third thing I want to improve is based on a comment from YouTuber TheRoscop13
[0:54] He’s pointed out that I could save some GPIO pins by using the same pins for the microphone and the amplifier board.
[1:01] And the final thing I’d like to do
[1:04] is wire up the shutdown pin on the amplifier board
[1:06] so it can be put into low power mode.
[1:09] Let fix all these issues.
[1:11] But first I’d like to thank the PCBWay for sponsoring this video
[1:15] PCBWay offer PCB Production
[1:18] CNC and 3D Printing
[1:20] PCB Assembly and much much more.
[1:22] They are great to deal with and offer excellent quality, service and value for money.
[1:26] Check out the link in the description.
[1:28] So let’s get on with the modifications.
[1:31] The first thing I’ll do is change the net ports to make them generic and remove the unneeded ones.
[1:38] I also need to add the SD line for the amplifier board
[1:42] this is really confusingly named as the two microphone boards use “SD” for serial data
[1:48] on the amplifier board, this is actually the shutdown and mode control pin.
[1:53] It combines a bunch of functions including selecting which channel the amplifier is on and selecting low power mode.
[2:02] With both the amplifier and microphones wired up,
[2:05] I can add the header for the remaining GPIO pins.
[2:09] I also find that I’m constantly running out of power and ground pins when hooking things up.
[2:14] So I’m going to add another header dedicated to this.
[2:17] This will give me 3 lines hooked up directly to the battery,
[2:20] 3 3v3 lines and 3 ground lines.
[2:25] With this all done we can update our current PCB and lay everything out again.
[2:31] The first thing I’ll do is hide the ground plane using “fn+shift+m” so we can see our traces more easily.
[2:37] I’d quite like to try and keep the board size the same as the existing one
[2:41] so I’m going to shift everything up to make room for the new headers.
[2:50] I’ll un-route all the existing traces as they are mostly all incorrect now.
[2:56] And I’ll switch off the ground net as this will be handled by our ground pours.
[3:01] We’re now ready to put down the tracks.
[3:06] I’m fairly easy in which pins are used for interfacing to the boards,
[3:09] so I’m quite happy to move them around to make the layout a bit easier.
[3:18] That’s all the signal lines wired up,
[3:21] I’ll add in the power lines now.
[3:24] I’ll make these a bit thicker than the signal traces.
[3:27] For the microphone power supply, this isn’t really important,
[3:30] but for the amplifier, it’s quite good as it can draw quite a bit of current when playing at full volume.
[3:36] 30 mil traces should be sufficient for our use case.
[3:40] I’ll also wire up the power header while I’m down in this part of the circuit board.
[3:45] With the VCC net complete, I’ll wire up all the GPIO pins.
[3:50] Once again I can see some simplifications by moving around pins.
[3:54] And now that I’ve started to wire it up, it feels like it would be much better to swap the power and GPIO header over.
[4:02] After a bit of position tweaking, our layout is almost complete.
[4:06] We can re-apply our copper pour and that should hook up all our ground nets.
[4:10] There is a slightly weird bug where the vias seem to forget which net they belong to,
[4:15] so I just need to set them to GND again.
[4:19] I also need to clean up the connections on the power headers from when I moved them.
[4:25] We’ll hide the ground pours using to make it a bit easier to see what is going on.
[4:31] And now with all done we have all our nets connected and we don’t have any DRC errors.
[4:37] I’ll just add a few more vias to stitch the two ground together.
[4:40] And to neaten things up I’ll redo the copper areas.
[4:44] I often find that leaving a layout for a few hours or even overnight triggers some thoughts
[4:50] and when you come back in the morning or a few hours later there are always some tweaks to make to your layout.
[4:59] In this case, after a nights sleep,
[5:01] I decided that I didn’t really need to make the board exactly the same size as before
[5:05] and making it a bit taller would let me label the GPIO pins.
[5:09] I think this is pretty important in any dev board, so I’m going to do it.
[5:14] I’m pretty happy with this layout now,
[5:16] a quick visual inspection to double-check that everything is wired up as it should be
[5:20] and we’re ready to submit the PCB to PCBWay
[5:23] We’ll download the Gerber file.
[5:25] And then we use the “PCB Instant Quote” option and click on the “Quick Order PCB” to upload our Gerber file.
[5:32] With the Gerber file uploaded, most of the options are set up for us
[5:36] and we can just click the Calculate button before proceeding to checkout.
[5:40] That’s it done
[5:41] this order will take a bit longer than usual as I’ve bundled it up with a board that is being SMT assembled.
[5:46] But normally you’ll get your PCB within 1-2 weeks depending on shipping.
[5:51] Thanks for watching!
[5:52] we’ll be putting this board to good use in some upcoming projects
[5:55] so don’t forget to subscribe and check back.