From 0944a27eb9eebcf402d482cfef42ddc46b06083a Mon Sep 17 00:00:00 2001
From: David Lechner <david@pybricks.com>
Date: Thu, 2 Jul 2020 21:06:26 -0500
Subject: [PATCH] increase firmware flashing packet size

---
 src/protocols/lwp3-bootloader.ts | 14 ++++++++++++--
 src/sagas/flash-firmware.ts      |  9 +++++++--
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/src/protocols/lwp3-bootloader.ts b/src/protocols/lwp3-bootloader.ts
index 413dc613..d4907413 100644
--- a/src/protocols/lwp3-bootloader.ts
+++ b/src/protocols/lwp3-bootloader.ts
@@ -63,8 +63,19 @@ export enum Result {
 
 /**
  * The largest allowable size for the payload of the ProgramFlash command.
+ *
+ * Theoretically, this is MTU - 9. However, City hub and Control+ hub report
+ * MTU of 158 but don't seem to be able to handle receiving that much data.
+ * Anything larger than 32 causes the bootloader to lock up.
  */
-export const MaxProgramFlashSize = 14;
+export const MaxProgramFlashSize: ReadonlyMap<HubType, number> = new Map<
+    HubType,
+    number
+>([
+    [HubType.MoveHub, 14],
+    [HubType.CityHub, 32],
+    [HubType.CPlusHub, 32],
+]);
 
 /**
  * Flash memory protection level.
@@ -111,7 +122,6 @@ export function createProgramFlashRequest(
     payload: ArrayBuffer,
 ): Uint8Array {
     const size = payload.byteLength;
-    assert(size <= MaxProgramFlashSize, 'payload is bigger than MaxProgramFlashSize');
     const msg = new Uint8Array(size + 6);
     const view = new DataView(msg.buffer);
     view.setUint8(0, Command.ProgramFlash);
diff --git a/src/sagas/flash-firmware.ts b/src/sagas/flash-firmware.ts
index b4984f87..388182ab 100644
--- a/src/sagas/flash-firmware.ts
+++ b/src/sagas/flash-firmware.ts
@@ -303,9 +303,14 @@ function* flashFirmware(action: FlashFirmwareFlashAction): Generator {
     }
 
     let count = 0;
+    const maxDataSize = MaxProgramFlashSize.get(info[0].hubType);
+    if (maxDataSize === undefined) {
+        // istanbul ignore next: indicates programmer error if reached
+        throw Error('Missing hub type in MaxProgramFlashSize');
+    }
 
-    for (let offset = 0; offset < firmware.length; offset += MaxProgramFlashSize) {
-        const payload = firmware.slice(offset, offset + MaxProgramFlashSize);
+    for (let offset = 0; offset < firmware.length; offset += maxDataSize) {
+        const payload = firmware.slice(offset, offset + maxDataSize);
         const programAction = (yield put(
             programRequest(info[0].startAddress + offset, payload.buffer),
         )) as BootloaderProgramRequestAction;