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Simulator: digitalReadPin always returns 0 when pin is clicked #7093
Description
Describe the bug
Arising from https://support.microbit.org/a/tickets/102932 (private)
In the simulator, clicking a pin that is being read with digital read pin no longer changes the value returned. pins.digitalReadPin() always returns 0, so programs that depend on digital input can't be tested in the simulator. See screenshot below.
To Reproduce
- Open this MakeCode project https://makecode.microbit.org/#pub:93153-38157-46980-90426, or create a new project with this code:
let reading = 0
basic.forever(function () {
reading = pins.digitalReadPin(DigitalPin.P0)
if (reading == 1) {
basic.showIcon(IconNames.Heart)
} else {
basic.clearScreen()
}
})- In the simulator, click P0 near the bottom of the pin. The pin label shows 0.
- Click P0 near the top of the pin. The pin label shows 1, but the heart never appears (see screenshot below).
Expected behavior
Clicking anywhere on the pin should set it as 1, the pin label should show 1 and the heart icon should be shown. I assume it should not have the slider effect like analogReadPin where clicking the bottom/top of pin gives a different value.
Screenshots
micro:bit version (please complete the following information):
not hardware related
Desktop (please complete the following information):
- OS: Mac
- Browser: Chrome
- Version
Likely cause
#6795 (commit a7e9261) changed the pin mouse and keyboard handlers in sim/visuals/microbit.ts so that digital input pins are capped at a value of 1:
let maxValue = pin.mode & PinFlags.Analog ? 1023 : 1;However, digitalReadPin in sim/state/edgeconnector.ts (and the equivalent in sim/state/edgeconnectorsim.ts) still uses a threshold of 100:
return pin.value > 100 ? 1 : 0;As a digital pin's value can now only be 0 or 1, this condition is never true and the read always returns 0.
For the slider effect on the digital pin, the click handler still maps click height to a value, Math.floor((400 - cursor.y) / 40 * maxValue).
Activity
abchatra commentedon Oct 1, 2026
Robert Knight (@microbit-robert) ?
microbit-matt-hillsdon commentedon Oct 2, 2026
We'll take a look at this one. Please can you assign to me?
martinwork commentedon Oct 12, 2026
Also reported in https://support.microbit.org/helpdesk/tickets/103321 (private).
martinwork commentedon Oct 26, 2026
Also reported in https://support.microbit.org/helpdesk/tickets/103630 (private)
martinwork commentedon Oct 30, 2026
Also reported in http://support.microbit.org/helpdesk/tickets/103593 (private)
Fix sim digitalReadPin and restore previous pin click areas
Fix sim digitalReadPin and make digital pins toggle switches
Fix sim digitalReadPin and split digital pin click areas in half
microbit-matt-hillsdon commentedon Oct 30, 2026
I've been looking at this and we have some choice as to how to proceed.
Using MakeCode v7 as a reference, mouse interaction with digital pins has a tiny area at the bottom that is 0 and the rest of the pin is 1. It's a slider but perhaps not so as anyone would notice for digital pins.
#6795 has flipped this, and a tiny area at the top goes to 1. Additionally, it's not correctly mapped to the pin value so even when we show 1 in the sim the program doesn't see it.
Options:
Richard Knoll (@riknoll) Abhijith Chatra (@abchatra) appreciate your thoughts. Whatever we do we'll need a fix to live.
riknoll commentedon Oct 30, 2026
i vote for toggle! slider doesn't really make any sense
microbit-matt-hillsdon commentedon Nov 3, 2026
Thanks Richard Knoll (@riknoll). Discussed with Jonny too and we're happy with that approach. I've opened #7117.
Fix sim digitalReadPin and make digital pins toggle switches (microso…
microbit-robert commentedon Nov 5, 2026
Richard Knoll (@riknoll) I've opened a PR to cherry-pick this fix to stable9.0 as it would be great to get this fix live to address the user feedback we've had. If the PR doesn't match convention, please feel free to close it and handle porting the change independently if convenient. Thanks!