ev3: Fix issues with flashing (some?) EV3s. #2352

jaguilar · 2025-12-20T04:46:43Z

Flash the EV3 all in one go rather than sector-by-sector. This appears to resolve issues we had with flashing (some?) EV3s, and mirrors what we do in pybricksdev.

Fixes pybricks/support#2375.

src/firmware/sagas.ts

laurensvalk · 2025-12-20T10:21:35Z

Fixes pybricks/support#2375.

This looks like a useful change, but it's a fix for a different problem 😄 In pybricks/support#2375 it never gets to flashing. It fails right away on getting the bad response to the get version command.

EDIT: I'll collect some notes in the issue thread instead.

Flash the EV3 all in one go rather than sector-by-sector. This appears to resolve issues we had with flashing (some?) EV3s, and mirrors what we do in pybricksdev.

dlech · 2025-12-23T19:31:23Z

src/firmware/sagas.ts

    );

-    const firmware = new Uint8Array(firmwareBase.length + 4);
+    const [checksumFunc, checksumSize] = (function () {


Suggested change

const [checksumFunc, checksumSize] = (function () {

const [checksumFunc, checksumExtraLength] = (function () {

As to not confuse with metadata['checkum-size'].

dlech · 2025-12-23T19:32:32Z

src/firmware/sagas.ts

-    })();
-
-    if (checksum === undefined) {
+    if (checksumFunc === undefined) {


Would make sense to move this to fail as early as possible (line 366).

dlech · 2025-12-23T19:36:06Z

src/firmware/sagas.ts

    );

-    const firmware = new Uint8Array(firmwareBase.length + 4);
+    const [checksumFunc, checksumSize] = (function () {


Suggested change

const [checksumFunc, checksumSize] = (function () {

const [checksumFunc, checksumSize] = (() => {

This code base typically uses lambda syntax.

dlech · 2025-12-23T19:38:27Z

src/firmware/sagas.ts

-            true,
-        )}, HW version: ${version.getUint32(4, true)}`,
-    );
+    // For reasons that we do not currently understand, some EV3s do not return


If we fail the get the version correctly, then can't we expect other responses to fail?

Seems like this needs more investigation.

In fact the other responses do not fail. I agree it warrants further investigation. Perhaps a new issue, though, since the method of flashing the firmware does not depend on the version?

dlech · 2025-12-23T19:39:20Z

src/firmware/sagas.ts

-    for (let i = 0; i < action.firmware.byteLength; i += sectorSize) {
-        const sectorData = action.firmware.slice(i, i + sectorSize);
-        assert(sectorData.byteLength <= sectorSize, 'sector data too large');
+    console.info(`Firmware size: ${action.firmware.byteLength} bytes`);


Suggested change

console.info(`Firmware size: ${action.firmware.byteLength} bytes`);

console.debug(`Firmware size: ${action.firmware.byteLength} bytes`);

Don't really need to spam the logs.

dlech · 2025-12-23T19:44:13Z

src/firmware/sagas.ts

+    erasePayload.setUint32(0, 0, true); // start address
+    erasePayload.setUint32(4, numSectors * sectorSize, true); // size
+    console.debug(
+        `Erasing bytes [0x${(0).toString(16)}, 0x${(numSectors * sectorSize).toString(


Would also be useful to log the number of sectors that we calculated.

dlech · 2025-12-23T19:44:40Z

src/firmware/sagas.ts

+    erasePayload.setUint32(0, 0, true); // start address
+    erasePayload.setUint32(4, numSectors * sectorSize, true); // size
+    console.debug(
+        `Erasing bytes [0x${(0).toString(16)}, 0x${(numSectors * sectorSize).toString(


Missing a - 1 on the end address?

dlech · 2025-12-23T19:46:48Z

src/firmware/sagas.ts

+    erasePayload.setUint32(0, 0, true); // start address
+    erasePayload.setUint32(4, numSectors * sectorSize, true); // size
+    console.debug(
+        `Erasing bytes [0x${(0).toString(16)}, 0x${(numSectors * sectorSize).toString(


IIRC, we also have a util function to add leading zeros in hex numbers.

dlech · 2025-12-23T19:49:52Z

src/firmware/sagas.ts

+    // Apparently, erasing a span of the flash creates some sort of record in
+    // the EV3, and we can only write within a given erase span. Writes that


I though that is what we were doing before. Erase one sector - write the entire one sector - erase the next sector - write one sector - and so on...

There has been quite a bit of testing and discussion about this already. Erasing the required space in one go was found to be more reliable. It's also what we've been testing with Pybricksdev.

Particularly here and here.

dlech · 2025-12-23T19:57:24Z

src/firmware/sagas.ts

+    // will hang on the last write we send.
+    const firmware = action.firmware;
+    for (let i = 0; i < firmware.byteLength; i += maxPayloadSize) {
+        const writeLength = Math.min(maxPayloadSize, firmware.byteLength - i);


Pretty sure this is redundant since slice doesn't pad thing but rather returns a partial if i + maxPayloadSize exceeds the firmware size.

dlech · 2025-12-23T22:13:08Z

It seems like this is fixing at least 3 different things. So would be better to split it up into 3 commits.

Fix not adding extra padding for non-existent checksum.
Change to erase all then flash all instead erase/flash one sector at a time.
Verify that the firmware blob size is exactly aligned to sector size.

laurensvalk reviewed Dec 20, 2025

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src/firmware/sagas.ts Outdated Show resolved Hide resolved

laurensvalk mentioned this pull request Dec 20, 2025

[Bug] EV3 firmware installation sends bad status values pybricks/support#2375

Open

jaguilar force-pushed the ev3-flash-fix branch from d1681a4 to 9cd1a76 Compare December 21, 2025 20:49

ev3: Fix issues with flashing (some?) EV3s.

e9e075f

Flash the EV3 all in one go rather than sector-by-sector. This appears to resolve issues we had with flashing (some?) EV3s, and mirrors what we do in pybricksdev.

jaguilar force-pushed the ev3-flash-fix branch from 9cd1a76 to e9e075f Compare December 23, 2025 03:06

dlech reviewed Dec 23, 2025

View reviewed changes

	const [checksumFunc, checksumSize] = (function () {
	const [checksumFunc, checksumExtraLength] = (function () {

	const [checksumFunc, checksumSize] = (function () {
	const [checksumFunc, checksumSize] = (() => {

	console.info(`Firmware size: ${action.firmware.byteLength} bytes`);
	console.debug(`Firmware size: ${action.firmware.byteLength} bytes`);

		// Apparently, erasing a span of the flash creates some sort of record in
		// the EV3, and we can only write within a given erase span. Writes that

ev3: Fix issues with flashing (some?) EV3s. #2352

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ev3: Fix issues with flashing (some?) EV3s. #2352

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jaguilar Dec 23, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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dlech commented Dec 23, 2025

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laurensvalk commented Dec 20, 2025 •

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