Using 74hct08 to move usb signal from one device to another

Projects Networking, Protocols, and Devices
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I am working on a PCB that has 2 ESP32-S3 on it and I was thinking of using a switch, together with 4 and-gates to redirect the signal to different microcontrollers. I found out, that the frequency of the usb-protocol is usually 12MHz but could also be more and I wanted to know if it is a good idea to use the 74hct08 IC or if there is another way for me to move the signals.

My implementation has one pin of the switch connected with D+ and D- on 2 gates, while the other pin is connected with them on 2 other gates. Both outputs of the switch are pulled down and the common pin is connected to 5V.

I could not find any help on this and the only idea that i had was to compare the period of the usb-protocol and the transition time of the IC. Anyone know if this would work? And if not, Should I use a Tri-State buffer instead?

2

USB is differential and bidirectional so an HCT08 would not work.
Use a switch intended for USB.
Why not just use a USB hub?

Here is one possible IC

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3

  • Have you considered using an FTDI module and then SN74LVCxxx gates.

  • When discussing a circuit show a schematic instead of texting a jumble of words.

4

Thank you for the recommendation. I was stupid. I completely forgot that the esp needs to send data back through the usb port.

5

My schematic is mixed up. I have split it into multiple sheets but the amount of elements on each sheet makes it hard to single out the circuit. I will upload pictures of the schematic from now on.

6

Has nothing to do with the ESP.
ALL USB communications send data both ways no matter which way you are sending.

7

just use a DPDT relay to switch D+ and D- between the 2 ESP...

one like these should do the trick IMHO https://uk.rs-online.com/web/p/hf-rf-relays/6839731P

8

An output from your CAD package would be prefered. Most can output an image file or a pdf.

9

From what I can see in the datasheet of the TS3USB221DRCR, OE is just to enable if the data is sent further or not. Correct me if I'm wrong, but could I simply connect it to ground? I was also wondering how exactly the S pin works. I'm guessing the input is connected to 1D+ and 1D- when S is low and with 2D+ and 2D- when S is high.

Datasheet:

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  • On the controller side of an FTDI chip, a couple SN74LVC2G66 gates can be configured as a transfer switch.
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Thank you for the recommendation. I have implemented the TS3USB221DRCR IC. However, I would still like to know how the S pin influences the output. If 1D+ and 1D- are connected to the output when S is 0 or 1.

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Also to consider is the data rates are negotiated between TWO devices at startup. A second device will NOT know the current data rate between the PC and the first device. Also you will NOT want to switch while a message transmission is in progress!

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Hello, That is not my intention. I use the switch to choose which microcontroller is connected to the USB connector. It will mostly communicate with only one of the 2 esp32, since the other is used as peripheral manager, so it will be programmed once with a bridging program, allowing the 1st esp32 to tell it which pins should be turned on and off.

14

  • I am only familiar with the ESP-WROOM-32

  • Can you connect the ESP32-S3 directly to USB differential signals ? :thinking:

15

Yes. It has a built-in USB to UART converter.

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  • Good to know
17

Yes

I'm guessing the input is connected to 1D+ and 1D- when S is low and with 2D+ and 2D- when S is high.

Yes

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image
image1342Ă—226 13.7 KB

When S=0

19

Why would it need to know?

20

Alright, thank you very much for the clarification