Enhancement: Allow ravedude to force the AVR to reset.

[ysterbal]

After falling over this a couple of times, I believe it might be a good idea to make things a little simpler for flashing to AVR when it requires a hard reset, but there is no explicit reset button, only a hard reboot.

The Adafruit ItsyBitsy 32u4-5V 16MHz board has a reset, but it uses the double-tap interface to reset to programming mode.

This meant I had to flash my binaries to the device manually jiggle the double press on the USB connection on both Linux and Windows and frankly, it's bloody annoying.

So I suggest we use the same approach the Arduino IDE uses: Open the port with BAUD 1200, which forces the device into programming mode, and then wait for n seconds and run the avrdude command.

In my testing, this works for most AVRs, but I would appreciate your thoughts before contributing my changes for this enhancement.

[stappersg]

On Sat, Dec 30, 2023 at 09:53:13AM -0800, Johan Van Zijl wrote: So I suggest we use the same approach the Arduino IDE uses: Open the port with BAUD 1200, which forces the device into programming mode, and then wait for n seconds and run the avrdude command. In my testing, this works for most AVRs, but I would appreciate your thoughts before contributing my changes for this enhancement.

Please describe the "trick" in more detail. I'm asking because I don't understand that only waiting with baudrate at 1200b/s on development host triggers programming mode. (I mis something like sending a character sequence (at 1200bd)). Groeten Geert Stappers -- Silence is hard to parse

[ysterbal]

So basically if you look at the code used in the Arduino IDE for programming the first thing it does is open the COM port with a 1200 baud this seems to basically reset the the device but basically only a soft reset, I am digging through the boot loader to understand it better right now but it works. Check out the code snippet here: https://github.com/arduino/Arduino/blob/master/arduino-core/src/cc/arduino/packages/uploaders/SerialUploader.java see line 130-136 Hope it helps.

[stappersg]

"Oh chips!"

[stappersg]

Below SerialUploader.java, line 139 are in comments the ingredients of the reset trick: The Watch Dog Timer, WDT and the Data Terminal Ready, DTR, line.

Elaboration on the "Oh chips!". There is hardware, do NOT ignore it. Grow from

Open the port with BAUD 1200

to

Toggle the DTR line, it is connected to the watch dog timer on the device

(to be continued)

[stappersg]

That "DTR line is connected to the watch dog timer on the device" is only true for some boards. Most likely for "arduino" boards. But avrdude is not "arduino"! And ravedude is a wrapper for avrdude, not for "arduino".

[Rahix]

And ravedude is a wrapper for avrdude, not for "arduino".

Sorry, but this is wrong. ravedude bridges the gap between avrdude, Rust, and specific AVR boards (including Arduino Boards). Otherwise, ravedude wouldn't take a board identifier like uno or nano to select the port and avrdude settings.

[ysterbal]

Understood for me, this was mainly around the Arduino, I have found the others to work just fine. That is why I wondered if we could support this as a feature. I did figure out it was hardware in the end, but thnx for the clarification, I might help others as well.

[ysterbal]

Just a note: this is actually dealt with in board.rs, and the only necessary thing is to add the ItsyBitsy 3v and 5v VID/PID

board.rs:

fn guess_port(&self) -> Option<anyhow::Result<std::path::PathBuf>> {
        Some(find_port_from_vid_pid_list(&[
            (0x2341, 0x0036),
            (0x2341, 0x8036),
            (0x239A, 0x000E),  // Support for ItsyBitsy 5V
            (0x239A, 0x000D),  // Support for ItsyBitsy 3V
            (0x2A03, 0x0036),
            (0x2A03, 0x8036),
        ]))
    }

Unless others need this, I am just going to keep this in my fork, so please consider this dealt with.

[Rahix]

Ah right, the Arduino Leonardo board code already includes the relevant line. @stappersg so it's crystal clear for you as well, we literally include the line

avr-hal/ravedude/src/board.rs

Line 174 in 7fc7911

match serialport::new(name.to_str().unwrap(), 1200).open() {

to do the "open port at 1200 baud".

---

Unless others need this, I am just going to keep this in my fork, so please consider this dealt with.

No no, I do want this included in upstream ravedude please! You certainly won't be the only one running into this. For the time being, my suggestion would be to simply duplicate the ArduinoLeonardo board code for ItsyBitsy and make it match the two ItsyBitsy VID:PID pairs. @ysterbal, would you be willing to send a pull-request for this?