Uploading to Nano 33 BLE without using the usb port

Hi

Since Nano 33 BLE has native USB port, I want to use it to transmit high bandwith sensor data to PC. So I have tried to upload sketch via UART (pin 1,2), with CP210x usb to ttl chip. However, the upload always end up timeout.

No device found on COM11
An error occurred while uploading the sketch

The result is the same regardless if I cannot the DTR pin pf CP210x to RST of Nano 33 BLE or not.

Thanks in advanced !

double reset would make more sense. boards with native USB don't use DTR for auto reset.
the bootloader listens only on USB.

Thanks for the reply. I tried disconnecting DTR, manual push button reset, etc. none of them worked.

Do I have to modify the bootloader to enable uploading from UART ?

Yes, I'm pretty sure you would need to modify the bootloader. Even though the Arduino API makes Serial and Serial1 seem like pretty much the same thing, they are actually very different in that Serial is a USB CDC serial port, while Serial1 is a UART. This is a different situation from the classic Nano, Uno, Mega, where Serial is a UART which is connected to a dedicated USB chip that creates the CDC serial port and acts as the bridge between that port and the UART on the primary microcontroller.

Actually you can't modify the Nano 33 BLE bootloader (or at leastt not easily) because it's not open source:

but check out that thread for some links to alternative bootloaders for the Nano 33 BLE.

Another option for you would be to connect a SWD programmer/debug probe to the test pads on the bottom of the Nano 33 BLE and use that for the uploads. The pinout is shown on the second page of this PDF:

Hi,
I have been using the Nano 33 BLE as well for some time now. I too would like to upload programs to it without using the default bootloader (using the SWD pins). Is it possible to use another Arduino as an SWD programmer?
I also came across the Adafruit DAP library but I am confused as to what boards it supports (Both as the target and as the programmer).
Any help would be appreciated :slight_smile:

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