Generate Resetsignal via DIO pin on the SWD for Targetsystem

[schnaggenhals]

Hello,

I would like to use your "One ROM Fire 28" product as an EPROM emulator in
an embedded system with a 68HC11. I think this will work.

My question is:

Is it possible to generate a reset signal via the DIO pin on the SWD port using a plugin?
This signal would halt the target system (/Reset) before uploading a new ROM image
and then release it after the upload by removing the reset signal.

(Reset - wait 10ms - upload new image - wait 10ms - release reset)

Of course, this would be done using a resistor and transistor connected at DIO-PIN.

Thank you in advance for your reply.

Best regards, Jörg

[piersfinlayson]

Probably not using the DIO pin, as the RP2350 only provides firmware with very limited external control of that pin.

But you could use image select A or image select B. They are only 3.3V tolerant on the 28 revs A1-4, so you would definitely need a transistor.

As the firmware reads these pins at boot to decide which image to boot you'd either need to install just a single image, or ensure your additional circuitry allows the pins to operate normally as inputs at boot. Once booted, and the plugin is started, the image select pins are no longer used.

There's no explicit API to do this yet, so you would need to set the pin to output, and set it high/low as required via the RP2350 hardware registers.

I do plan to provide this function (ability to set an image select pin to output high/low) via the USB stack - not sure when yet.

[schnaggenhals]

Thank you for your message.

I thought you could use the signal "SWCLK" or "SWDIO" for this.

Then I could pick up the voltage signal of the status LED (signal LED0) for the reset control.
The target system requires a LOW level of reset input.
With a suitable additional circuit (I know what I'm doing) at the end with a transistor (open collector) create the reset.
The LED on the ONE-ROM can be controlled via a plugin.

Thank you in advance for your reply.

Greetings Jörg

[piersfinlayson]

I thought you could use the signal "SWCLK" or "SWDIO" for this.

You mean control the GPIOs via the SWD lines using a debug probe, either directly or via a plugin? Yes, you could do this.

Or you could use USB to drive the plugin, and avoid having to use SWD.

Then I could pick up the voltage signal of the status LED (signal LED0) for the reset control.

Yes this would work, but why use the LED rather than the Sel A or Sel B pins? Those are already broken out.

The target system requires a LOW level of reset input.
With a suitable additional circuit (I know what I'm doing) at the end with a transistor (open collector) create the reset.
The LED on the ONE-ROM can be controlled via a plugin

[schnaggenhals]

Hello Piers,

First of all, thank you very much for your answers and congratulations on ONE-ROM.

I guess I didn't formulate my first question correctly.

I intend to use ONE-ROM as a classic EPROM emulator with reset output for my target system (68HC11).
So I only need a ROM file stored in the ONE-ROM, which I can compile.
I can do without several ROM images stored in ONE-ROM and thus
SEL_A (GPIO26) or SEL_B (GPIO27) free for my application.
Before and during the update, the target system should be informed of the generated reset can be stopped.
After updating the ROM file, the reset should be lifted.
I wasn't sure if this works with SEL_A (GPIO26) or SEL_B (GPIO27) via a plugin.
This makes everything a little easier for me, because I can use the RESET circuit (resistor and transistor) with an adaptor
on the post strip.

Thank you for your clarification.

Greetings Jörg

[piersfinlayson]

Yes, this should work today (via SEL A and B) with a plugin, although you'll need to access the GPIOs directly via RP2350 hardware registers, as I haven't exposed via a plugin API yet. I'll get this into the USB plugin at some point, so it can all be done directly using USB and the CLI, rather than requiring a separate plugin, but no timescales yet!