firmware/sagas: reduce BLE firmware burst size

Mac users have recently been reporting failed firmware updates due to
the hub disconnecting during the update process. This is likely due to
the Mac sending packets faster than the hub can handle. This changes
the arbitrary BLE firmware burst size from 10 to 8 to reduce the chance
of the hub getting overwhelmed.

Fixes: pybricks/support#1787

CHANGELOG.md

@@ -4,6 +4,11 @@
 
 ## [Unreleased]
 
+### Fixed
+- Fixed Bluetooth firmware updates sometimes failing on macOS. ([support#1787])
+
+[[support#1787]]: https://github.com/pybricks/support/issues/1787
+
 ## [2.3.0-beta.1] - 2023-11-24
 
 ### Changed

src/firmware/sagas.test.ts

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-// Copyright (c) 2021-2022 The Pybricks Authors
+// Copyright (c) 2021-2024 The Pybricks Authors
 
 import {
     FirmwareMetadata,
@@ -200,12 +200,12 @@ describe('flashFirmware', () => {
                     break;
                 }
 
-                if (count % 10 === 0) {
+                if (count % 8 === 0) {
                     action = await saga.take();
                     expect(action).toEqual(checksumRequest(++id));
 
                     saga.put(didRequest(id));
-                    saga.put(checksumResponse(0));
+                    saga.put(checksumResponse(0xee));
                 }
             }
 
@@ -366,7 +366,7 @@ describe('flashFirmware', () => {
                     break;
                 }
 
-                if (count % 10 === 0) {
+                if (count % 8 === 0) {
                     action = await saga.take();
                     expect(action).toEqual(checksumRequest(++id));
 
@@ -1331,12 +1331,12 @@ describe('flashFirmware', () => {
                     break;
                 }
 
-                if (count % 10 === 0) {
+                if (count % 8 === 0) {
                     action = await saga.take();
                     expect(action).toEqual(checksumRequest(++id));
 
                     saga.put(didRequest(id));
-                    saga.put(checksumResponse(0));
+                    saga.put(checksumResponse(0xeb));
                 }
             }
 
@@ -1507,12 +1507,12 @@ describe('flashFirmware', () => {
                     break;
                 }
 
-                if (count % 10 === 0) {
+                if (count % 8 === 0) {
                     action = await saga.take();
                     expect(action).toEqual(checksumRequest(++id));
 
                     saga.put(didRequest(id));
-                    saga.put(checksumResponse(0));
+                    saga.put(checksumResponse(0xeb));
                 }
             }
 
@@ -1689,7 +1689,7 @@ describe('flashFirmware', () => {
                     break;
                 }
 
-                if (count % 10 === 0) {
+                if (count % 8 === 0) {
                     action = await saga.take();
                     expect(action).toEqual(checksumRequest(++id));
 
@@ -2254,12 +2254,12 @@ describe('flashFirmware', () => {
                 break;
             }
 
-            if (count % 10 === 0) {
+            if (count % 8 === 0) {
                 action = await saga.take();
                 expect(action).toEqual(checksumRequest(++id));
 
                 saga.put(didRequest(id));
-                saga.put(checksumResponse(0));
+                saga.put(checksumResponse(0xeb));
             }
         }
 

src/firmware/sagas.ts

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-// Copyright (c) 2020-2022 The Pybricks Authors
+// Copyright (c) 2020-2024 The Pybricks Authors
 
 import {
     FirmwareReader,
@@ -529,11 +529,11 @@ function* handleFlashFirmware(action: ReturnType<typeof flashFirmware>): Generat
                 break;
             }
 
-            // Request checksum every 10 packets to prevent buffer overrun on
+            // Request checksum every 8 packets to prevent buffer overrun on
             // the hub because of sending too much data at once. The actual
             // number of packets that can be queued in the Bluetooth chip on
             // the hub is not known and could vary by device.
-            if (count % 10 === 0) {
+            if (count % 8 === 0) {
                 const checksumAction = yield* put(checksumRequest(nextMessageId()));
 
                 const { response } = yield* all({
@@ -543,7 +543,7 @@ function* handleFlashFirmware(action: ReturnType<typeof flashFirmware>): Generat
 
                 if (response.checksum !== runningChecksum) {
                     // istanbul ignore next
-                    if (process.env.NODE_ENV !== 'test') {
+                    if (process.env.NODE_ENV === 'test') {
                         console.error(
                             `checksum: got ${hex(response.checksum, 2)} expected ${hex(
                                 runningChecksum,