VUSB/D+/D- pads question Teensy 4.1

A

acarson

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Hi im trying to bypass the usb micro port with a usb-c cable. The original cable was a usb-c to usb micro. I cut off the micro end and soldered the red wire of the cable to the Teensy VUSB through hole port. I soldered the green wire to the D+ pad, the white wire to D- pad and the black wire to gnd. When I plug the usb plug into power it does not power the teensy.

Note: the usb micro receptacle is still attached to the teensy and the Vin/Vusb pads have not been cut (I read that you don't need to separate them if you're powering though VUSB and not VIN).

What am I missing or doing wrong here? Also please let me know if there is an easier way to do this. My end goal is to essentially replace the usb micro socket with usb-c that can supply both power and data without using an adapter
 
USB-C has a couple of pulldown resistors on the slave end that allow the host to detect that a slave device has been attached before it will supply power. As a guess, perhaps the adapter cable had these resistors molded into the Micro-B end which has now been cut off so the host doesn't see a slave and so no power is being supplied?

If power is being supplied, perhaps you need to swap the D+/D- though they are usually connected as you have done.

If you are doing a PCB baseboard, the usual way to convert the Micro B to USB-C is to use pogo pins to connect the D+/D- pads to the baseboard where the USB-C connector is located and add the the necessary resistors there.
 
Investing. this is more so trying to figure out a good circuit for my pcb design in regards to usb-c. My idea is for a 16-pin usb-c female receptical. The receptacle will have all vbus lines ties to each other, as well as all gnd tied together. The CC pins will individually each go through a 5.11K resistor to gnd. Both D+ pins will be linked together then go to the teensy D+ pad. Both D- pins will also be linked together then go to the teensy D- pad. The VBUS pads after being linked will hit a .1uf capacitor to ground, then a ferrite bead (220ohm@100mhz), then a 10uf cap to ground, and finally into an on-off toggle being sent to Teensy VBUS pin.

Does that seem like a circuit that would work?
 
Might work with Teensy 4.1, where the bottom side pads are the USB device D+ and D-.

But on Teensy 4.0 the bottom side D+ and D- are USB host, not USB device. Space is extremely limited on Teensy 4.0 and a lot of signals are made available. There just wasn't space like on Teensy 4.1 to bring the USB host signals to ordinary pins, so the compromise was made to put them on the bottom. But USB device D+ and D- can't also fit, so those just aren't available as bottom side pads on Teensy 4.0.
 
Your wiring setup sounds fine to me. You can route the power to either the VUSB or 5V pin if the trace between them is still intact and you are powering the setup only from USB.

The Teensy includes a 2.2uF cap on the power pins. The maximum capacitance per the USB spec is 10uF to keep inrush current down. I think adding a 10uF cap will be fine, but you could go down to something like a 6.8uF if you wanted to be sure to stay safely within specs.

If you want to be able to power the Teensy separately with or without USB being connected, then you would want to cut the trace between the VUSB and 5V pads and add a Schottky diode between the VUSB and 5V pins with the cathode facing the 5V pin. This diode can be mounted on the back of the Teensy across the VUSB/5V pads or it can be on the baseboard.

In this case you would route the USB power to the VUSB pin and the external power to the 5V pin. That external power would also need an inline Schottky diode with the cathode facing the 5V pin. That allows you to power the setup from either the USB or an external source and if they are both connected at the same time, the one with the higher voltage will safely power the setup.
 
I would just want to power the teensy 4.1 through the usb-c receptacle via the VUSB pin. With this setup would I need any ssd protection on the VUSB, D+ and D- lines? I think I read that Teensy 4.1 already has that built in, but I just wanna be sure
 
The Teensy 4.1 does not implement any additional protection components on the Micro-B USB. The signals connect directly from the connector to the processor. I am also not aware of anyone reporting electrical damage to a Teensy via the USB connection.

When I did a baseboard with a remotely mounted USB-C, I took the same strategy and just connected the data lines straight through with no extra components, being careful to length match and run them close together. I have had no issues with that setup which has seen moderate usage.

In an ideal implementation, adding ESD protection diodes and such can't hurt and may be a good idea especially if there is not much control over what gets plugged into the port.
 
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