Fix P15 clone print failures (empty labels / power-off crash)

packages/core/src/device/profiles/p12.ts

@@ -37,6 +37,7 @@ export const p12Profile: DeviceProfile = {
   packetSize: 90,
   flowControl: {
     initialCredits: 4,
+    packetDelayMs: 30,
   },
   defaults: { density: 2, paperType: "gap" },
   namePrefixes: ["P12", "LP90", "P11"],

packages/core/src/device/profiles/p15.ts

@@ -25,6 +25,7 @@ export const p15Profile: DeviceProfile = {
   packetSize: 95,
   flowControl: {
     initialCredits: 4,
+    packetDelayMs: 30,
   },
   defaults: { density: 2, paperType: "gap" },
   namePrefixes: [

packages/core/src/printer.ts

@@ -244,8 +244,14 @@ export class Printer {
     } else if (response.type === "mtu") {
       const mtu = response.value as number;
       if (mtu > 3) {
-        debugLog("BLE", `mtu=${mtu} packet=${mtu - 3}`);
-        this.flowController.setPacketSize(mtu - 3);
+        const mtuPacketSize = mtu - 3;
+        // Cap at profile-specified size — the profile knows what the device
+        // firmware can handle; a higher BLE MTU doesn't mean the printer's
+        // application-level buffer can keep up with larger writes.
+        const cap = this.profile.packetSize;
+        const effective = cap ? Math.min(mtuPacketSize, cap) : mtuPacketSize;
+        debugLog("BLE", `mtu=${mtu} packet=${effective}${cap && mtuPacketSize > cap ? ` (capped from ${mtuPacketSize})` : ""}`);
+        this.flowController.setPacketSize(effective);
       }
     }
 

packages/core/src/transport/flow-control.ts

@@ -5,7 +5,7 @@ import { debugLog } from "../debug-log.js";
 
 const DEFAULT_OPTIONS: FlowControlOptions = {
   initialCredits: 4,
-  starvationTimeoutMs: 30,
+  starvationTimeoutMs: 1000,
   timerIntervalMs: 5,
   packetDelayMs: 0,
 };
@@ -35,7 +35,10 @@ export class FlowController {
   /** Reset credits to initial state before a new print job. */
   reset(): void {
     this.credits = this.options.initialCredits;
-    this.hasRealCredits = false;
+    // Preserve hasRealCredits — it reflects whether this device supports
+    // credit-based flow control, which is a connection-level property.
+    // Clearing it would let starvation recovery bypass flow control at the
+    // start of every print job.
     this.lastCreditTime = Date.now();
     debugLog("FC", `reset, credits=${this.credits}`);
   }
@@ -61,9 +64,15 @@ export class FlowController {
     let offset = 0;
     debugLog("TX", `sending ${data.length}B in ${Math.ceil(data.length / this.packetSize)} packets, credits=${this.credits}`);
 
+    const { packetDelayMs } = this.options;
+
     while (offset < data.length) {
       await this.waitForCredit();
 
+      if (packetDelayMs > 0 && offset > 0) {
+        await new Promise((r) => setTimeout(r, packetDelayMs));
+      }
+
       const remaining = data.length - offset;
       const chunkSize = Math.min(remaining, this.packetSize);
       const chunk = data.subarray(offset, offset + chunkSize);