u/Environmental_Bad724

Hey everyone. First-time PCB design here for a homemade digital watch project that I am working on. My hope is to make a nice 3D printed digital watch with an ePaper display. Any suggestions, improvements, or answers to my questions would be greatly appreciated!

I currently have a 4-layer PCB ((1)signal, (2)GND, (3)PWR, (4)signal). To give some more background to what I am working with, here is a list of my major components, their intended functions, and datasheets:

1. ATMEGA328PB-AU-ND (U1): my MCU on the board.
2. LSM303AHTR (U4): digital compass module. Intend to use this for a compass direction display on my watch. https://www.st.com/content/ccc/resource/technical/document/datasheet/1b/a1/fd/09/9f/41/44/cf/DM00177690.pdf/files/DM00177690.pdf/jcr:content/translations/en.DM00177690.pdf
3. XC6206P182MR-G (U3): LDO to step my 3.3V battery source down to 1.8V to power the above digital compass module (yes I probably should've found a digital compass that runs off 3.3V to save me the trouble). https://product.torexsemi.com/system/files/series/xc6206.pdf
4. PCA9306DCTR (U2): Level shifter to allow I2C between my 3.3V MCU and the 1.8V digital compass. https://www.ti.com/lit/ds/symlink/pca9306.pdf?ts=1757540593801
5. RV-8803-C7 (U6): Crystal oscillator RTC with temperature compensation. Using this for low-power timekeeping that only wakes up the rest of the components (via INT) every minute to update the minute reading on the display. Won't show seconds unless the user holds the button in order to conserve battery. https://www.microcrystal.com/fileadmin/Media/Products/RTC/Datasheet/RV-8803-C7.pdf
6. TMP117MAIDRVR (U5): Temp sensor. Placed it near the edge of the board. Intend to put a small port covered with a Gore-Tex membrane (to waterproof) near it for higher accuracy. https://www.ti.com/lit/ds/symlink/tmp117.pdf
7. TL6340AF160Q (S1): Edge mount button. Intent is to have the display show the temperature reading, compass heading, and seconds when the button is held. May come up with some creative button pressing scheme to allow setting alarms etc. https://configured-product-images.s3.amazonaws.com/Datasheets/TL6340.pdf
8. 89898-303ALF (J1): 6-pin ISP connector. Using this to do the programming on the board. May remove it after to save vertical space during installation.
9. BU2032SM-JJ-GTR(BT1): Coin cell holder. Currently have on underside of board.
10. 24 pin ZIF connector (J2): This is what introduces most of the complexity into my design. It is the connector that connects to my eInk display (ER-EPD0154-2) via ribbon cable. The eInk display has an on-board Display Driver (SSD1681) which requires an external voltage booster circuit. That is what necessitates the 3 diodes, transistor, inductor, etc near the 24 pin connector. https://www.buydisplay.com/download/manual/ER-EPD0154-2_Datasheet.pdf?srsltid=AfmBOoqM5LeeL7_UdtmfCszjST-iRqtlVPpcBnYFIvL_sQ7yFUJ9JqX6 https://cdn-learn.adafruit.com/assets/assets/000/099/573/original/SSD1681.pdf

Main Questions:

1. Does my voltage-booster circuit look correct? Are there any EMI concerns with it and the close proximity to all the signal traces nearby?
2. I resorted to running a lot of the signal traces between the 24pin connector and my MCU through VIAs and to the underside of the board so that the voltage booster lines could cross on the top signal layer. Is this a fine practice?
3. My second layer is an uninterrupted GND plane, and my third layer is 3.3V PWR plane. I've also poured ground on both signal layers. Is this best practice?
4. I drop some traces through vias to run through the PWR plane for a few connections. Is this best practice, or would I be better off dropping these to the bottom signal layer?
5. In a couple places I run traces underneath some components. Is this fine? I've heard a lot of different things from different people online regarding this.
6. I also placed some pull-up resistors and decoupling caps from the 24 pin connector onto the bottom signal layer in order to clear up clutter and fit everything there. Is this acceptable?

Thank you in advance for any help or advice! Excited to hopefully be get this printed sometime soon.

Hey everyone. First-time PCB design here for a homemade digital watch project that I am working on. My hope is to make a nice 3D printed digital watch with an ePaper display. Any suggestions, improvements, or answers to my questions would be greatly appreciated!

I currently have a 4-layer PCB ((1)signal, (2)GND, (3)PWR, (4)signal). To give some more background to what I am working with, here is a list of my major components, their intended functions, and datasheets:

1. ATMEGA328PB-AU-ND (U1): my MCU on the board.
2. LSM303AHTR (U4): digital compass module. Intend to use this for a compass direction display on my watch. https://www.st.com/content/ccc/resource/technical/document/datasheet/1b/a1/fd/09/9f/41/44/cf/DM00177690.pdf/files/DM00177690.pdf/jcr:content/translations/en.DM00177690.pdf
3. XC6206P182MR-G (U3): LDO to step my 3.3V battery source down to 1.8V to power the above digital compass module (yes I probably should've found a digital compass that runs off 3.3V to save me the trouble). https://product.torexsemi.com/system/files/series/xc6206.pdf
4. PCA9306DCTR (U2): Level shifter to allow I2C between my 3.3V MCU and the 1.8V digital compass. https://www.ti.com/lit/ds/symlink/pca9306.pdf?ts=1757540593801
5. RV-8803-C7 (U6): Crystal oscillator RTC with temperature compensation. Using this for low-power timekeeping that only wakes up the rest of the components (via INT) every minute to update the minute reading on the display. Won't show seconds unless the user holds the button in order to conserve battery. https://www.microcrystal.com/fileadmin/Media/Products/RTC/Datasheet/RV-8803-C7.pdf
6. TMP117MAIDRVR (U5): Temp sensor. Placed it near the edge of the board. Intend to put a small port covered with a Gore-Tex membrane (to waterproof) near it for higher accuracy. https://www.ti.com/lit/ds/symlink/tmp117.pdf
7. TL6340AF160Q (S1): Edge mount button. Intent is to have the display show the temperature reading, compass heading, and seconds when the button is held. May come up with some creative button pressing scheme to allow setting alarms etc. https://configured-product-images.s3.amazonaws.com/Datasheets/TL6340.pdf
8. 89898-303ALF (J1): 6-pin ISP connector. Using this to do the programming on the board. May remove it after to save vertical space during installation.
9. BU2032SM-JJ-GTR(BT1): Coin cell holder. Currently have on underside of board.
10. 24 pin ZIF connector (J2): This is what introduces most of the complexity into my design. It is the connector that connects to my eInk display (ER-EPD0154-2) via ribbon cable. The eInk display has an on-board Display Driver (SSD1681) which requires an external voltage booster circuit. That is what necessitates the 3 diodes, transistor, inductor, etc near the 24 pin connector. https://www.buydisplay.com/download/manual/ER-EPD0154-2_Datasheet.pdf?srsltid=AfmBOoqM5LeeL7_UdtmfCszjST-iRqtlVPpcBnYFIvL_sQ7yFUJ9JqX6 https://cdn-learn.adafruit.com/assets/assets/000/099/573/original/SSD1681.pdf

Main Questions:

1. Does my voltage-booster circuit look correct? Are there any EMI concerns with it and the close proximity to all the signal traces nearby?
2. I resorted to running a lot of the signal traces between the 24pin connector and my MCU through VIAs and to the underside of the board so that the voltage booster lines could cross on the top signal layer. Is this a fine practice?
3. My second layer is an uninterrupted GND plane, and my third layer is 3.3V PWR plane. I've also poured ground on both signal layers. Is this best practice?
4. I drop some traces through vias to run through the PWR plane for a few connections. Is this best practice, or would I be better off dropping these to the bottom signal layer?
5. In a couple places I run traces underneath some components. Is this fine? I've heard a lot of different things from different people online regarding this.
6. I also placed some pull-up resistors and decoupling caps from the 24 pin connector onto the bottom signal layer in order to clear up clutter and fit everything there. Is this acceptable?

Thank you in advance for any help or advice! Excited to hopefully be get this printed sometime soon.