feat: add BLE support for ESP32-C3 via BTDM VHCI

ble.go

@@ -0,0 +1,138 @@
+//go:build esp32c3
+
+package espradio
+
+/*
+#include "espradio.h"
+*/
+import "C"
+
+import (
+	"errors"
+	"runtime"
+	"runtime/interrupt"
+	"time"
+	"unsafe"
+)
+
+// bleArenaPoolSize is the arena the BT controller allocates from.
+//
+// Note: the boot log shows the 10 ADV DATA TX buffers and 12 ACL TX buffers
+// coming back NULL with their EM_BASE_REG LUT entries set to 0x3fc00000, and the
+// DB heap getting 0 bytes. That looks like arena exhaustion but is not — raising
+// this to 96 KB reproduced the identical 22 NULLs, so those EM regions are
+// allocated lazily (on first advertise / first connection) and the 0x3fc00000
+// bases are simply "unmapped". Left at the WiFi size.
+const bleArenaPoolSize = arenaPoolSize
+
+// VHCITransport provides HCI read/write access to the ESP32 BLE controller
+// via the Virtual HCI interface. It implements the transport interface
+// expected by the tinygo bluetooth package.
+type VHCITransport struct{}
+
+// Buffered returns the number of bytes available to read from the controller.
+func (t VHCITransport) Buffered() int {
+	return int(C.espradio_vhci_buffered())
+}
+
+// ReadByte reads a single byte from the HCI controller.
+func (t VHCITransport) ReadByte() (byte, error) {
+	for {
+		b := int(C.espradio_vhci_read_byte())
+		if b >= 0 {
+			return byte(b), nil
+		}
+		runtime.Gosched()
+	}
+}
+
+// Read reads up to len(buf) bytes from the HCI controller.
+func (t VHCITransport) Read(buf []byte) (int, error) {
+	if len(buf) == 0 {
+		return 0, nil
+	}
+	for {
+		n := int(C.espradio_vhci_read((*C.uint8_t)(unsafe.Pointer(&buf[0])), C.int(len(buf))))
+		if n > 0 {
+			return n, nil
+		}
+		runtime.Gosched()
+	}
+}
+
+// Write sends an HCI packet to the BLE controller.
+func (t VHCITransport) Write(buf []byte) (int, error) {
+	if len(buf) == 0 {
+		return 0, nil
+	}
+	n := int(C.espradio_vhci_write((*C.uint8_t)(unsafe.Pointer(&buf[0])), C.int(len(buf))))
+	return n, nil
+}
+
+// BLEInit initializes the BLE controller on the ESP32-C3.
+// Must be called before using VHCITransport.
+func BLEInit() error {
+	// Ensure radio hardware is powered up (clocks, power domain, modem reset).
+	// This is normally done by Enable() for WiFi, but BLE may be used standalone.
+	if err := initHardware(); err != nil {
+		return err
+	}
+
+	// Ensure arena allocator is initialized. The BT blob needs malloc for
+	// internal function tables. If WiFi Enable() was already called, this
+	// is a no-op (arenaPool is already set).
+	if arenaPool == nil {
+		arenaPool = makeArenaPool(bleArenaPoolSize)
+		C.espradio_arena_init((*C.uint8_t)(unsafe.Pointer(&arenaPool[0])), C.size_t(len(arenaPool)))
+	}
+
+	// Start scheduler ticker if not already running (provides periodic
+	// execution for the BLE controller task goroutine via kickSched).
+	if isrKick == nil {
+		startSchedTicker()
+	}
+
+	// Wire BT interrupts before controller init
+	setupBTInterrupts()
+
+	// Initialize the BLE controller (C side):
+	//   bt_clock → rom_data_init → osi_register → controller_init → phy_enable → controller_enable → vhci
+	res := int(C.espradio_ble_init())
+	if res != 0 {
+		return errors.New("espradio: BLE init failed")
+	}
+
+	// Enable hardware interrupts for BT
+	C.espradio_bt_enable_hw_interrupts()
+
+	// Give the controller task time to stabilize
+	time.Sleep(100 * time.Millisecond)
+
+	return nil
+}
+
+// ─── BT Interrupt Handlers ───────────────────────────────────────────────────
+
+// CPU interrupt numbers for BT (must match esp32c3/isr.c)
+const (
+	btCPUInt5 = 28 // RWBT + BT_BB → CPU interrupt 28
+	btCPUInt8 = 30 // RWBLE → CPU interrupt 30
+)
+
+func setupBTInterrupts() {
+	// Register and enable Go interrupt handlers (like WiFi does).
+	// Enable() sets priority=5 and edge-triggered, then
+	// espradio_bt_enable_hw_interrupts() overrides to priority=7 + level-triggered.
+	intr5 := interrupt.New(btCPUInt5, btISR5Handler)
+	intr5.Enable()
+	intr8 := interrupt.New(btCPUInt8, btISR8Handler)
+	intr8.Enable()
+}
+
+func btISR5Handler(interrupt.Interrupt) {
+	C.espradio_bt_isr_dispatch_5()
+}
+
+func btISR8Handler(interrupt.Interrupt) {
+	C.espradio_bt_isr_dispatch_8()
+}