FTDI Community
General Category => Discussion - Hardware => Topic started by: jmuellers on February 11, 2021, 10:39:35 AM
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Dear FTDI community members,
this is my first time posting in the community, and I hope I have debugged my design with enough care to be eligible to ask for your support.
My background in PCB development is 5+ years.
I have uploaded a PDF showing the schematic, screenshots of the four PCB layers, the Altium PCB file, a photograph of the board, and the USB Treeview log.
Unfortunately the size restrictions for the attachments make it impossible to upload them all here. Please find them in this owndrive share with Password "ftdi":
https://uni-bonn.sciebo.de/s/lRxJRAeBovjzGSR
My goal is to build a USB-4x-UART bridge, and I believe I followed the datasheet section 6.1 in my implementation.
Please note:
(1.1) The circuit "USB power" is not populated since it could not work like that. Instead, VUSBPRE and VUSBSW are directly connected.
(1.2) The lines TX/RX 1...4 are open at the moment.
What I see is that the device is not enumerating. Please find the output of USB TreeView attached.
Things I verified
(2.1) 3.3V and 1.8V are present. No ringing or noise on the power lines, also not after the ferrites.
(2.2) Quartz is running with 12MHz.
(2.3) Resetn is high.
(2.4) At powerup current briefly goes up to around 70mA as expected, then drops to below 1mA.
Things I have tried
(3.1) Populate a second board with the same design. The result is the same. This leads me to believe that a hardware defect is unlikely, as I used new components.
(3.2) Changing cap sizes for the quartz, since I misinterpreted the unregular operation of the quartz for a defect (when in fact I probably just observed the FT4232 going to sleep after unsuccessful connetion to the host, and attempting re-enumeration).
(3.3) The circuit is self-powered, 3.3V are supplied from a TPS73801 throught the 5V USB supply. This part was working with a previous FT232X prototype. Still I have tried to supply 3.3V externaly with a lab supply, but the result is unchanged.
(3.4) Try different USB ports, also directly attached (without hub). Try differenct computer.
(3.5) Remove EEPROM and adjacent resistors (this is shown on the photograph). No change.
(3.6) Try different USB cables.
(3.7) Repeatedly plug in/out.
(3.8) Remove USB_SH from board GND (hence the scrateches aroudn the USB connector)
Things I suspect
(4.1) The clock traces in L2 right below the EECS and EECLK pads are certainly not ideal. Did I say 5+ years of experience? Well...
I am looking forward to any ideas you might have.
Thanks,
Johannes
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Hello,
Can you please email your local support team which will allow you to attach your files?
https://ftdichip.com/technical-support/ (https://ftdichip.com/technical-support/)
It looks like you have used the wrong resistor/capacitor values on the USB data lines for edge rate control.
Please refer to AN_146 USB Hardware Design Guidelines for FTDI ICs (https://ftdichip.com/wp-content/uploads/2020/08/AN_146_USB_Hardware_Design_Guidelines_for_FTDI_ICs.pdf).
You can also refer to our Development modules for reference which include schematics:
FT4232H Mini-Module (https://ftdichip.com/products/ft4232h-mini-module/)
FT4232H-56 Mini-Module (https://ftdichip.com/products/ft4232h-56-mini-module/)
Best Regards,
FTDI Community
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Dear FTDI support,
how embarassing. I did not notice the simple fact that FT4232 is high-speed instead of full-speed (in fact I had never worked with high-speed USB). Removing the caps has solved my issue at once.
Thank you!
Johannes
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Hello,
Great glad you got it working.
This will help other FTDI Community users with similar issues.
Ensure that you have 10 ohm resistors on the USB data lines (not 27 ohm) as well.
Best Regards,
FTDI Community