Flashing Locally on Photon - Difference between --serial and --usb

General
1

In the Documentation I see two ways of Flashing locally.

  1. Compiling remotely and flashing locally
  2. Flashing your program locally via USB

Both if these work for the Photon. However only #2 is listed for the Photon and #1 is listed for the Electron. So my questions are:

  1. What is the difference (to my Photon) if any?
  2. Which one is the recommended way for the Photon?
  3. What am I missing or is it just that that documentation needs to be updated?
2

Flashing with -usb uses dfu-util to upload code to your device. Your device must be in dfu mode (flashing yellow) to accept firmware.

Flashing with -serial is only available for the Electron I believe, and the Electron must be in listening mode (breathing blue) to accept firmware. It does so by opening a serial port and sending the firmware without requiring dfu-util to be installed on your computer.

Flashing with -usb using dfu-util is seen as the “correct” way for flashing firmware. It is more reliable, and all Particle devices can go into dfu mode and accept firmware.

I think the docs just need to be updated.

3

Nope, this also works for the Photon (both versions should work on all Particle devices).
But I'd always go for DFU Mode flashing via particle flash --usb firmware.bin since --serial always reports success on any file that can be sent (irrespective of its content) but --usb gives you proper feedback whether this was a suitable file and if the code got flashed OK.

4

Thank you @nrobinson2000 and @ScruffR for your replies. So I guess the docs need to be updated and using DFU is the better choice (if one has the DFU Utility installed and working).

I had an issue yesterday where I used method #1 (listen mode and Serial) and it seemed like the device was flashed OK, but things didn’t work as expected. @ScruffR, your answer explains why.

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