espnet: WIP support for on-chip WiFi on an ESP32C3

Work in progress. Does not work yet.

Some notes:

  - This requires some changes to TinyGo, look at the espnet branch.
  - The  next step is probably defining all the functions in
    g_wifi_osi_funcs (see espnet.c). Right now it hangs in
    esp_wifi_init_internal, probably a NULL pointer dereference.
  - This is only for the ESP32-C3. This will require some work to work
    on other chips from Espressif.

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "espnet/esp-idf"]
+	path = espnet/esp-idf
+	url = https://github.com/espressif/esp-idf.git

espnet/ap.go

@@ -0,0 +1,40 @@
+package espnet
+
+/*
+#cgo CFLAGS: -DCONFIG_IDF_TARGET_ESP32C3
+#cgo CFLAGS: -Iinclude
+#cgo CFLAGS: -Iesp-idf/components/esp_common/include
+#cgo CFLAGS: -Iesp-idf/components/esp_event/include
+#cgo CFLAGS: -Iesp-idf/components/esp_netif/include
+#cgo CFLAGS: -Iesp-idf/components/esp_wifi/include
+
+#cgo LDFLAGS: -Lesp-idf/components/esp_wifi/lib/esp32c3 -lnet80211 -lpp -lphy -lmesh -lcore
+#cgo LDFLAGS: -Tesp-idf/components/esp_rom/esp32c3/ld/esp32c3.rom.ld
+
+#include "esp_private/wifi.h"
+#include "esp_wifi_types.h"
+#include "espnet.h"
+*/
+import "C"
+
+type ESPWiFi struct {
+}
+
+var WiFi = &ESPWiFi{}
+
+type Config struct {
+}
+
+var internalConfig = C.wifi_init_config_t{
+	osi_funcs: &C.g_wifi_osi_funcs,
+}
+
+func (wifi ESPWiFi) Configure(config Config) error {
+	return makeError(C.esp_wifi_init_internal(&internalConfig))
+}
+
+func (wifi ESPWiFi) AccessPointMAC() ([6]byte, error) {
+	var mac [6]byte
+	errCode := C.esp_wifi_get_mac(C.ESP_IF_WIFI_AP, &mac[0])
+	return mac, makeError(errCode)
+}

espnet/error.go

@@ -0,0 +1,103 @@
+package espnet
+
+// #include <esp_err.h>
+// #include <esp_wifi.h>
+import "C"
+
+// Wrapper for C.esp_err_t. Don't convert a C.esp_err_t to an Error type,
+// instead use makeError to handle ESP_OK.
+type Error C.esp_err_t
+
+// makeError converts a C.esp_err_t into an error or nil depending on whether
+// errCode indicates an error or not.
+func makeError(errCode C.esp_err_t) error {
+	if errCode == C.ESP_OK {
+		return nil
+	}
+	return Error(errCode)
+}
+
+func (e Error) Error() string {
+	switch {
+	case e < C.ESP_ERR_WIFI_BASE:
+		// esp-idf/components/esp_common/include/esp_err.h
+		switch e {
+		case C.ESP_OK:
+			return "OK" // not an error
+		case C.ESP_FAIL:
+			return "ESP FAIL"
+		case C.ESP_ERR_NO_MEM:
+			return "Out of memory"
+		case C.ESP_ERR_INVALID_ARG:
+			return "Invalid argument"
+		case C.ESP_ERR_INVALID_STATE:
+			return "Invalid state"
+		case C.ESP_ERR_INVALID_SIZE:
+			return "Invalid size"
+		case C.ESP_ERR_NOT_FOUND:
+			return "Requested resource not found"
+		case C.ESP_ERR_NOT_SUPPORTED:
+			return "Operation or feature not supported"
+		case C.ESP_ERR_TIMEOUT:
+			return "Operation timed out"
+		case C.ESP_ERR_INVALID_RESPONSE:
+			return "Received response was invalid"
+		case C.ESP_ERR_INVALID_CRC:
+			return "CRC or checksum was invalid"
+		case C.ESP_ERR_INVALID_VERSION:
+			return "Version was invalid"
+		case C.ESP_ERR_INVALID_MAC:
+			return "MAC address was invalid"
+		default:
+			return "Unknown error"
+		}
+	case e >= C.ESP_ERR_WIFI_BASE && e < C.ESP_ERR_MESH_BASE:
+		// esp-idf/components/esp_wifi/include/esp_wifi.h
+		switch e {
+		case C.ESP_ERR_WIFI_NOT_INIT:
+			return "WiFi driver was not installed by esp_wifi_init"
+		case C.ESP_ERR_WIFI_NOT_STARTED:
+			return "WiFi driver was not started by esp_wifi_start"
+		case C.ESP_ERR_WIFI_NOT_STOPPED:
+			return "WiFi driver was not stopped by esp_wifi_stop"
+		case C.ESP_ERR_WIFI_IF:
+			return "WiFi interface error"
+		case C.ESP_ERR_WIFI_MODE:
+			return "WiFi mode error"
+		case C.ESP_ERR_WIFI_STATE:
+			return "WiFi internal state error"
+		case C.ESP_ERR_WIFI_CONN:
+			return "WiFi internal control block of station or soft-AP error"
+		case C.ESP_ERR_WIFI_NVS:
+			return "WiFi internal NVS module error"
+		case C.ESP_ERR_WIFI_MAC:
+			return "MAC address is invalid"
+		case C.ESP_ERR_WIFI_SSID:
+			return " SSID is invalid"
+		case C.ESP_ERR_WIFI_PASSWORD:
+			return "Password is invalid"
+		case C.ESP_ERR_WIFI_TIMEOUT:
+			return "Timeout error"
+		case C.ESP_ERR_WIFI_WAKE_FAIL:
+			return "WiFi is in sleep state(RF closed) and wakeup fail"
+		case C.ESP_ERR_WIFI_WOULD_BLOCK:
+			return "The caller would block"
+		case C.ESP_ERR_WIFI_NOT_CONNECT:
+			return "Station still in disconnect status"
+		case C.ESP_ERR_WIFI_POST:
+			return "Failed to post the event to WiFi task"
+		case C.ESP_ERR_WIFI_INIT_STATE:
+			return "Invalid WiFi state when init/deinit is called"
+		case C.ESP_ERR_WIFI_STOP_STATE:
+			return "Returned when WiFi is stopping"
+		case C.ESP_ERR_WIFI_NOT_ASSOC:
+			return "The WiFi connection is not associated"
+		case C.ESP_ERR_WIFI_TX_DISALLOW:
+			return "The WiFi TX is disallowed"
+		default:
+			return "Other WiFi error"
+		}
+	default:
+		return "Other error"
+	}
+}

espnet/espnet.c

@@ -0,0 +1,98 @@
+#include <stdint.h>
+#include <stddef.h>
+#include <stdio.h>
+#include "espnet.h"
+
+// OS adapter functions.
+// See: esp-idf/components/esp_wifi/include/esp_private/wifi_os_adapter.h
+wifi_osi_funcs_t g_wifi_osi_funcs = {
+    ._version = ESP_WIFI_OS_ADAPTER_VERSION,
+    // TODO: define these functions.
+    ._magic = ESP_WIFI_OS_ADAPTER_MAGIC,
+};
+
+// This is a string constant that is used all over ESP-IDF and is also used by
+// libnet80211.a. The main purpose is to be a fixed pointer that can be compared
+// against etc.
+const char *WIFI_EVENT = "WIFI_EVENT";
+
+// Required by libphy.a
+int phy_printf(const char *format, ...) {
+    va_list args;
+    va_start(args, format);
+    printf("phy: ");
+    int res = vprintf(format, args);
+    va_end(args);
+    return res;
+}
+
+// Required by libpp.a
+int pp_printf(const char *format, ...) {
+    va_list args;
+    va_start(args, format);
+    printf("pp: ");
+    int res = vprintf(format, args);
+    va_end(args);
+    return res;
+}
+
+// Required by libnet80211.a
+int net80211_printf(const char *format, ...) {
+    va_list args;
+    va_start(args, format);
+    printf("net80211: ");
+    int res = vprintf(format, args);
+    va_end(args);
+    return res;
+}
+
+// Source: esp-idf/components/wpa_supplicant/src/utils/common.c
+static int hex2num(char c)
+{
+	if (c >= '0' && c <= '9')
+		return c - '0';
+	if (c >= 'a' && c <= 'f')
+		return c - 'a' + 10;
+	if (c >= 'A' && c <= 'F')
+		return c - 'A' + 10;
+	return -1;
+}
+
+// Source: esp-idf/components/wpa_supplicant/src/utils/common.c
+int hex2byte(const char *hex)
+{
+	int a, b;
+	a = hex2num(*hex++);
+	if (a < 0)
+		return -1;
+	b = hex2num(*hex++);
+	if (b < 0)
+		return -1;
+	return (a << 4) | b;
+}
+
+// Source: esp-idf/components/wpa_supplicant/src/utils/common.c
+/**
+ * hexstr2bin - Convert ASCII hex string into binary data
+ * @hex: ASCII hex string (e.g., "01ab")
+ * @buf: Buffer for the binary data
+ * @len: Length of the text to convert in bytes (of buf); hex will be double
+ * this size
+ * Returns: 0 on success, -1 on failure (invalid hex string)
+ */
+int hexstr2bin(const char *hex, uint8_t *buf, size_t len)
+{
+	size_t i;
+	int a;
+	const char *ipos = hex;
+	uint8_t *opos = buf;
+
+	for (i = 0; i < len; i++) {
+		a = hex2byte(ipos);
+		if (a < 0)
+			return -1;
+		*opos++ = a;
+		ipos += 2;
+	}
+	return 0;
+}

espnet/espnet.h

@@ -0,0 +1,4 @@
+#include <stdbool.h>
+#include "esp_private/wifi_os_adapter.h"
+
+extern wifi_osi_funcs_t g_wifi_osi_funcs;

examples/espnet/main.go

@@ -0,0 +1,20 @@
+package main
+
+import "tinygo.org/x/drivers/espnet"
+
+func main() {
+	err := espnet.WiFi.Configure(espnet.Config{})
+	if err != nil {
+		println("failed to configure:", err.Error())
+	}
+	mac, err := espnet.WiFi.AccessPointMAC()
+	if err != nil {
+		println("failed to read MAC address:", err.Error())
+		return
+	}
+	print("MAC address:")
+	for _, b := range mac {
+		print(" ", b)
+	}
+	println()
+}