2 KNOMI's will not power on by USB-C connection to computer or show up in device list

[bigtreetech]

2 KNOMI's will not power on by USB-C connection to computer or show up in device list

[sprior]

I was using a USB-C to USB-C cable to plug them into my computer. By any chance is a USB-A (computer) to USB-C (KNOMI) cable required to make it work?

[M4dMike]

Had the same issue, USB-A to USB-C works for me, Knomi is showing up in device manager as "USB-SERIAL CH340 (COM3)"

Did you manage to get to a working state? I am struggling with flashing, as uploading the firmware fails...

A fatal error occurred: Failed to connect to ESP32: No serial data received.

[Malygros]

I was using a USB-C to USB-C cable to plug them into my computer. By any chance is a USB-A (computer) to USB-C (KNOMI) cable required to make it work?

Did you mange do get it work? Got the same error. Even with USB-A to USB-C.
USB-SERIAL CH340 (COM4) is recognized in the device Manager.

[sprior]

It's been working for me with a USB-C to USB-A cable, though the requirement to use one isn't documented anywhere that I've seen. I also have to hold the boot button before plugging it in, then it's recognized by the flash utility in PlatformIO.

[Fragmon]

I cant connect too. Is this possible that knomi make a Mistake with tracing? They add a 10k on 3.3V not gnd

[M4dMike]

@Fragmon Nope, it's correct and it works fine after all.
If you want to set it into boot mode, disconnect it from power, press the button an plug it in while the button is pressed

[sprior]

@M4dMike Flash mode only works with a USB-A to USB-C cable for me when connecting to my laptop. If I use a USB-C to USB-C cable the KNOMI doesn't get power at all when in boot mode or not. That same USB-C to USB-C cable works with a USB-C power supply.

[M4dMike]

@sprior Same for me. I was referring to the pull up/down resistor.

[Fragmon]

@Fragmon Nope, it's correct and it works fine after all. If you want to set it into boot mode, disconnect it from power, press the button an plug it in while the button is pressed

I know this:) but it dont change the Mode. It's always in serial. We measure with Multimeter and the path is correct. The pin goes to gnd while Pressing.

[sprior]

@M4dMike I am not at all an expert on this, but I think I've heard that USB-C devices use resistors to signal their need for power or ability to provide it. So I thought @Fragmon's comment about resistors not being correct might be related to power delivery and not the ability to enter boot mode. It could also explain why a USB-A to USB-C cable would work and a USB-C to USB-C does not.

[Ybalrid]

all I know is that the modem control signals from the serial are not able to reset the device from the USB port. You need to press the boot button to upload new firmware, and once new firmware is uploaded, you need to disconnect and reconnect the device for it to startup again.