12/23/2025 10 AM - work on PSU design and USB HUB design schematics

My streaming Hub will require 5v of power that will supply somewhere between 3A of current , and some parts of the hub require 3.3V

I am using a CM4(raspeberry Pi) as the compute module , but I am working on a custom carrier board .

It will include a PSU - this will have a USB -C power source and regulator to step down to 3.3V

I already designed the PSU although i am yet to make final adjustments , I also started worked on the USB HUb and HDMI

12/23/2025 4 PM - FInished USB Hub IC

I finished up my USB HUb IC..
I added ESD protection for the USB ports and for host to HUb connection
I also put power switchs for the USB ports.
I made sure I added capacitors and resistore where needed

12/27/2025 - ESD for HDMI , CM4 core cleanup , USB-C modifications

Finally got the schematic where it needs to be.

The big win today was the getting my USB-C and Hub coordination right . I initially forgot i needed to be a ble to flash my os so I had to modify the USB-C port to handle both PD power and Flashing mode, but the real trick was ensuring the USB Hub doesn't clash with the data lines while I'm trying to flash the eMMC.

In order to avoid this , I ensured I connceted the resetN pin of my USBhub to the nRPIBOOT of my cm4 , now when I enable it , my USB C automatically disappears from the board and i can flash wiyhout worries.

I also spent a lot of time on ESD protection. I added dedicated ESD chips to the HDMI lines so that a simple static shock from plugging in a monitor won't fry the CM4. Along with that, I integrated power switches into the design so I have actual control over the hardware states instead of just letting the rails fly.

On the CM4 pinout, I did a massive "spring cleaning." I went through the 200-pin connector and properly terminated everything. I added NCs to all the fluff (CSI, DSI, etc.) and made sure the essentials like the 1.8V loopback and PCIe clock request pull-ups were locked in.

The schematic looks like its finally where i want it to be , I'm still considering other things like wether to inlude ethernet or not , so Its not completely locked in

.

12/29/2025 12 PM - I'm cooked

Woke up to wrap up my schematic and then I found out I was cooked...

Opened kicad and tried opening my project folder it gave me an error , I laughed it off , Kicad must be a standup comedian it's so funny I thought ...

After 3 more trials and being met with the same error , it dawned on me and I started to take this more seriously

I turned to google and reddit , my knight in shining armor i thought , well I was wrong nothing i tried worked..

tried editing the file in a text editor it turned out null, checked my backups and opened them , Empty!!!!

then the real pnic started , I began to understand that days worth of work have vanished , tried extarcting the zipped back up files , boom Archive corrupted .

And so I came to the conclusion that I am cooked...
Deadline is in 2 days , what can I do, well I have decided that I will build again ....

will it be hard ?? yes painstakingly even , but will I do it ?? you sure bet I would .....

wish me Luck guys

12/29/2025 3 PM - FInished USB_C PD

I decided to switch to the CM5, so I spent time sourcing new components and carefully studying the CM5 datasheet. Within a relatively short time, I was able to design a new PSU to match the updated requirements.

As before, the PSU handles both power delivery and flashing. I’ve added ESD protection to guard against static discharge, along with decoupling and bulk capacitors for noise filtering and improved power stability. I also included bleeder resistors to ensure the system discharges quickly, allowing the board to power off immediately when external power is removed.

12/30/2025 - Completed USB HUB , Navigations and HDMI

I completed the USB hub section using the USB2514B, just like before. I added three USB-A ports to support peripherals and bootable drives, with ESD protection on each port to prevent static discharge.

I kept individual power switches for each USB-A port, using the AP2171W, to provide controlled power and protection per port. I also included the required 24 MHz crystal. The hub’s RESET_N pin is connected to the CM5 nRPIBOOT pin so that during flashing, the hub is disabled and does not conflict with the USB-C interface.

For navigation, I switched from simple push buttons to dual-contact push switches for more reliable input and better signal handling.

The power button uses a TS-1010A-B switch connected between GND and the PWR_BUT pin on the CM5.

The HDMI section remained mostly the same, but I changed the ESD device to the PUSB3F96X because it is better suited for high-speed HDMI signals due to its low capacitance.

12/31/2025 11 AM - Added Ethernet and LEDs for status

I decided to include Ethernet as a fallback connection. Since Wi-Fi is not always guaranteed to be reliable—especially during early bring-up—it made sense to add Ethernet as a fail-safe option.

I added ESD protection on the Ethernet lines to protect against static discharge. I also included the required series resistors and LED connections for the Ethernet status and activity indicators.

For the CM5 status indicators, I used dedicated power and activity LEDs. The power LED is driven through a U602 (SN74LVC1G14DBVR), which is used as a Schmitt-trigger inverter to buffer and clean the control signal, ensuring a stable and well-defined LED drive.

Both the power and activity indicators use D6 green LEDs, to provide clear visual feedback for system power and activity.

12/31/2025 1 PM - ERC run and board cleanup

After rounding up all the connections, I ran ERC, reviewed the warnings and errors, and fixed them accordingly. At this point, it’s safe to say the schematic is complete. I’ll continue to review it and seek feedback from others in case there are any mistakes to correct or potential improvements to make.