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vault backup: 2026-06-27 16:08:27

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PCB Design/Music Player/Process.md
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@@ -50,8 +50,8 @@ $$R = \frac{{3.3 - 3.0}}{0.16} = 1.875 \Omega$$
For a standard value a $2.0 \Omega$ resistor will be used. This may make the display a little bit less bright but won't change it very much.Vs - Vf) / If using the maximum forward voltage:
### Backlight Control
Since this device will be battery-powered and the display is not needed most of the time it needs to be able to be controlled by software by the ESP32-S3. To do this a transistor will be added to the cathode pins to control the backlight with an io pin from the microcontroller.
I chose [this mosfet](https://www.digikey.com/en/products/detail/infineon-technologies/IRLML2502TRPBF/811439) since it has very low resistance and should turn off and on with the 3.3V logic levels of the esp32-s3.
I chose [this mosfet](https://www.digikey.com/en/products/detail/infineon-technologies/IRLML2502TRPBF/811439) since it has very low resistance and should turn off and on with the 3.3V logic levels of the ESP32-S3.
## USB
There are a few considerations needed for effectively routing USB. The first is inline resistors for the data lines. Based on the hardware design guidelines $22\Omega$ resistors were chosen. The hardware design guidelines also suggest adding footprints for capacitors to ground on the data lines which were also added. These can be populated later to help match impedance although they will likely not be needed.
## MicroSD Card
There are two different modes that can be used to read and write data to the microSD card, SPI and SD-MMC. SPI is simpler but SD-MMC can get faster speeds and is supported by the ESP32-S3 so that is what I will be using. the ESP32-S3 can multiplex this functionality to any of the GPIO pins so the pinout of the microcontroller is not important. 10K pullup resistors are also needed on the CMD and data lines for the micro SD card to ensure that they do not enter an undefined state. I have also included a 10K pullup resistor on the card detect
There are two different modes that can be used to read and write data to the microSD card, SPI and SD-MMC. SPI is simpler but SD-MMC can get faster speeds and is supported by the ESP32-S3 so that is what I will be using. the ESP32-S3 can multiplex this functionality to any of the GPIO pins so the pinout of the microcontroller is not important. 10K pullup resistors are also needed on the CMD and data lines for the micro SD card to ensure that they do not enter an undefined state. I have also included a 10K pullup resistor on the card detect pin so that it is easier for the microcontroller to read and the in is in a defined state when there is no card in the slot (the pin is pulled to ground when there is a card inserted).