drivers/edbg_eui: add driver to get MAC address from Atmel EDBG

The EDBG debugger on the `samr21-xpro` contains a unique 64 bit address
intended to be used as a MAC address for the internal radio.

This adds a driver to read that EUI-64 from the debugger, it should match
with the MAC address printed on the label on the board.

drivers/Makefile.dep

@@ -241,6 +241,10 @@ ifneq (,$(filter dynamixel,$(USEMODULE)))
   USEMODULE += uart_half_duplex
 endif
 
+ifneq (,$(filter edbg_eui,$(USEMODULE)))
+  FEATURES_REQUIRED += periph_i2c
+endif
+
 ifneq (,$(filter enc28j60,$(USEMODULE)))
   FEATURES_REQUIRED += periph_gpio
   FEATURES_REQUIRED += periph_gpio_irq

drivers/edbg_eui/Makefile

@@ -0,0 +1 @@
+include $(RIOTBASE)/Makefile.base

drivers/edbg_eui/edbg_eui.c

@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2020 Benjamin Valentin
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     drivers_edbg_eui
+ *
+ * @{
+ * @file
+ * @brief       Driver for getting a unique ID from the Atmel Embedded Debugger.
+ *
+ * @author      Benjamin Valentin <benjamin.valentin@ml-pa.com>
+ *
+ * @}
+ */
+
+#include "edbg_eui.h"
+#include "periph/i2c.h"
+#include "net/l2util.h"
+
+#ifndef EDBG_I2C_DEV
+#define EDBG_I2C_DEV I2C_DEV(0)
+#endif
+
+#define EDBG_ADDR   (0x28)
+#define TOKEN_EUI64 (0xD2)
+#define TOKEN_EXT   (0xE1)
+
+int edbg_get_eui64(eui64_t *addr)
+{
+    int res = 0;
+    i2c_acquire(EDBG_I2C_DEV);
+
+    /* dummy read for another token - following edbg user manual, section 4.3.1
+     * only returns the EUI-64 once, this work-around works reliable though.
+     */
+    if ((res = i2c_read_regs(EDBG_I2C_DEV, EDBG_ADDR, TOKEN_EXT, addr, 2, 0))) {
+        goto out;
+    }
+
+    /* EDBG provides an EUI-64 for the internal radio */
+    if ((res = i2c_read_regs(EDBG_I2C_DEV, EDBG_ADDR, TOKEN_EUI64, addr, sizeof(*addr), 0))) {
+        goto out;
+    }
+
+out:
+    i2c_release(EDBG_I2C_DEV);
+    return res;
+}

drivers/include/edbg_eui.h

@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2020 Benjamin Valentin
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @defgroup    drivers_edbg_eui Driver for getting MAC address out of Atmel EDBG
+ * @ingroup     drivers_misc
+ * @brief       Device driver interface for the AT24MAC I2C chip
+ * @{
+ *
+ * @file
+ *
+ * @author      Benjamin Valentin <benjamin.valentin@ml-pa.com>
+ */
+
+#ifndef EDBG_EUI_H
+#define EDBG_EUI_H
+
+#include <stdint.h>
+#include "net/eui64.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief   Get the unique EUI64 address from a Atmel EDBG debugger
+ *
+ * @param[out] addr     memory location to copy the address into.
+ *
+ * @return              0 on success, error otherwise.
+ */
+int edbg_get_eui64(eui64_t *addr);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* EDBG_EUI_H */
+/** @} */

tests/driver_edbg_eui/Makefile

@@ -0,0 +1,8 @@
+BOARD ?= samr21-xpro
+BOARD_WHITELIST = samr21-xpro
+
+include ../Makefile.tests_common
+
+USEMODULE += edbg_eui
+
+include $(RIOTBASE)/Makefile.include

tests/driver_edbg_eui/main.c

@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2020 Benjamin Valentin
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     tests
+ * @{
+ *
+ * @file
+ * @brief       Test application for the EDBG EUI driver
+ *
+ * @author      Benjamin Valentin <benjamin.valentin@ml-pa.com>
+ *
+ * @}
+ */
+
+#include <stdio.h>
+#include "edbg_eui.h"
+
+static int test_get_eui64(void)
+{
+    eui64_t e64;
+    if (edbg_get_eui64(&e64) != 0) {
+        puts("[FAILED]");
+        return 1;
+    }
+
+    printf("EUI-64:");
+    for (unsigned i = 0; i < sizeof(e64.uint8); ++i) {
+        printf(" %02x", e64.uint8[i]);
+    }
+    puts("");
+
+    return 0;
+}
+
+int main(void)
+{
+    if (test_get_eui64()) {
+        return -1;
+    }
+
+    puts("[SUCCESS]");
+
+    return 0;
+}