| Index > teleproject > Refactored the PCB to accomodate the NRF wireless chip | |
|---|---|
| Author/Date | Refactored the PCB to accomodate the NRF wireless chip |
| memecode 24/07/2024 11:55am | The original PCB only really allowed for analog input. But now that I've pretty much decided to stick with the NRF24L01 wireless instead of Wifi I need to be able to hook that up to the ESP32 at the same time as getting 30 analog inputs. I've had to sacrifice 2 inputs (32 -> 30) to steal a GPIO pin for the NRF's 5 SPI pins. But that's ok I only have 30 keys anyway. It does mean though I can't have a volume and / or expression on the guitar. Which was probably asking too much anyway so I'm not that fussed. I plan to use a foot based expression pedal for volume anyway for the most part.
This is the revised schematic:  And the layout of the PCB itself looks like:  Much cleaner topology this time. I'm finding what works and applying that. Like it's much better to keep all the horizontal traces on the same side of the PCB, and all the vertical on the other. Allows lots of cross overs without tearing your hair out. Also I made sure to group the input pins on the mux chips into corresponding blocks of 4 pins on the U5/U6 headers. By make the headers into 2x8 groups instead of 1x16 it's all a lot more compact. The whole PCB is smaller than before. Which is nice. |
| memecode 26/07/2024 9:45am | I was mulling over whether to pull the trigger on getting this board fabbed and then realized that some functionality that I'm going to really need it missing. Which comes down to 2 things:
1) There is no inputs left to read the state of the pickup/keyboard switch. The player needs to be able to select between the magnetic guitar pickups and the keyboard with a 3 way toggle switch. And the ESP32 needs to be able to sense that switches position and change what it's sending to the laptop. 2) There is no output pins left to show status. I think it's going to be super important to see the status of the wireless link and via an LED: Red if the power is on, orange if the wifi is up and maybe green if it's getting some acknowledgement from the software on the laptop that the connection is good. So I'd need at least 2 pins for that. All up I need 3 more pins and none are available. So what to do? Well currently I have 2 banks of 16 analog inputs (needing 17 pins: 1 bank select and 16 inputs). What if I had 4 banks of 8 (needing 10 pins, 2 for bank select and 8 inputs)? Because that would free up a bunch of IO pins for other things. I'll need to go and find 1:4 analog mux chips. And redo all the schematic and PCB, but I think it's the way forward. |
| Reply | |