From 6b0082bb3fa86583062225c2faf9b78fde9c317b Mon Sep 17 00:00:00 2001
From: Marian Buschsieweke <marian.buschsieweke@ovgu.de>
Date: Fri, 22 Mar 2019 17:50:08 +0100
Subject: [PATCH] shell: Add command i2c_scan

Add a trivial shell program that scans for all slaves on an I2C bus by iterating
all of the possible 127 I2C addresses and checking for the ACK of the device.
---
 makefiles/pseudomodules.inc.mk      |   1 +
 sys/Makefile.dep                    |   4 +
 sys/shell/commands/Makefile         |   4 +
 sys/shell/commands/sc_i2c_scan.c    | 112 ++++++++++++++++++++++++++++
 sys/shell/commands/shell_commands.c |   7 ++
 5 files changed, 128 insertions(+)
 create mode 100644 sys/shell/commands/sc_i2c_scan.c

diff --git a/makefiles/pseudomodules.inc.mk b/makefiles/pseudomodules.inc.mk
index d4057d8e78..165d9e1be0 100644
--- a/makefiles/pseudomodules.inc.mk
+++ b/makefiles/pseudomodules.inc.mk
@@ -35,6 +35,7 @@ PSEUDOMODULES += gnrc_sixlowpan_router
 PSEUDOMODULES += gnrc_sixlowpan_router_default
 PSEUDOMODULES += gnrc_sock_check_reuse
 PSEUDOMODULES += gnrc_txtsnd
+PSEUDOMODULES += i2c_scan
 PSEUDOMODULES += l2filter_blacklist
 PSEUDOMODULES += l2filter_whitelist
 PSEUDOMODULES += lis2dh12_spi
diff --git a/sys/Makefile.dep b/sys/Makefile.dep
index ce7f6f2c82..f9afc587e3 100644
--- a/sys/Makefile.dep
+++ b/sys/Makefile.dep
@@ -2,6 +2,10 @@ ifneq (,$(filter eepreg,$(USEMODULE)))
   FEATURES_REQUIRED += periph_eeprom
 endif
 
+ifneq (,$(filter i2c_scan,$(USEMODULE)))
+  FEATURES_REQUIRED += periph_i2c
+endif
+
 ifneq (,$(filter prng_fortuna,$(USEMODULE)))
   CFLAGS += -DCRYPTO_AES
 endif
diff --git a/sys/shell/commands/Makefile b/sys/shell/commands/Makefile
index 6c41e53ca9..d7d860a0a1 100644
--- a/sys/shell/commands/Makefile
+++ b/sys/shell/commands/Makefile
@@ -77,4 +77,8 @@ ifneq (,$(filter periph_rtc,$(USEMODULE)))
   SRC += sc_rtc.c
 endif
 
+ifneq (,$(filter i2c_scan,$(USEMODULE)))
+  SRC += sc_i2c_scan.c
+endif
+
 include $(RIOTBASE)/Makefile.base
diff --git a/sys/shell/commands/sc_i2c_scan.c b/sys/shell/commands/sc_i2c_scan.c
new file mode 100644
index 0000000000..2ef6b63dea
--- /dev/null
+++ b/sys/shell/commands/sc_i2c_scan.c
@@ -0,0 +1,112 @@
+/*
+ * Copyright (C) 2019 Otto-von-Guericke-Universität Magdeburg
+ *
+ * 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     sys_shell_commands
+ * @{
+ *
+ * @file
+ * @brief       An I2C bus scanner
+ *
+ * @author      Marian Buschsieweke <marian.buschsieweke@ovgu.de>
+ *
+ * @}
+ */
+
+#include <errno.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "board.h"
+#include "periph/i2c.h"
+
+static int get_dev(i2c_t *dev, int argc, char **argv)
+{
+    if (argc == 2) {
+        int idx = atoi(argv[1]);
+        if ((idx < 0) || (idx >= (int)I2C_NUMOF)) {
+            printf("I2C device with number \"%s\" not found\n", argv[1]);
+        }
+        else {
+            *dev = I2C_DEV(idx);
+            return 0;
+        }
+    }
+    printf("Usage: %s [DEVICE_NUMBER]\n", argv[0]);
+    return -1;
+}
+
+static inline int is_addr_reserved(uint16_t addr)
+{
+    if ((addr < 0x0e) || (addr > 0x77))
+        return 1;
+
+    return 0;
+}
+
+int _i2c_scan(int argc, char **argv)
+{
+    i2c_t dev;
+    if (get_dev(&dev, argc, argv)) {
+        return -1;
+    }
+
+    printf("Scanning I2C device %s...\n", argv[1]);
+    if (i2c_acquire(dev)){
+        puts("Failed to acquire I2C device");
+        return -1;
+    }
+
+    puts(
+        "addr not ack'ed = \"-\", addr ack'ed = \"X\", addr reserved = \"R\", error = \"E\"\n"
+        "     0 1 2 3 4 5 6 7 8 9 a b c d e f"
+    );
+
+    for (char i = 0; i < 8; i++) {
+        char row[] = { '0', 'x', '0' + i, '0', '\0' };
+        fputs(row, stdout);
+        uint16_t addr = i;
+        addr <<= 4;
+        for (unsigned j = 0; j < 16; j++) {
+            char str[] = { ' ', '-', '\0' };
+            if (is_addr_reserved(addr)) {
+                str[1] = 'R';
+            }
+            else {
+                char dummy[1];
+                int retval;
+                while (-EAGAIN == (retval = i2c_read_byte(dev, addr, dummy, 0))) {
+                    /* retry until bus arbitration succeeds */
+                }
+
+                switch (retval) {
+                    case 0:
+                        /* success: Device did respond */
+                        str[1] = 'X';
+                        break;
+                    case -ENXIO:
+                        /* No ACK --> no device */
+                        break;
+                    default:
+                        /* Some unexpected error */
+                        str[1] = 'E';
+                        break;
+                }
+            }
+
+            fputs(str, stdout);
+            addr++;
+        }
+        puts("");
+    }
+
+    i2c_release(dev);
+    return 0;
+}
diff --git a/sys/shell/commands/shell_commands.c b/sys/shell/commands/shell_commands.c
index b0b689810a..176e76cd98 100644
--- a/sys/shell/commands/shell_commands.c
+++ b/sys/shell/commands/shell_commands.c
@@ -145,6 +145,10 @@ extern int _cord_ep_handler(int argc, char **argv);
 extern int _app_metadata_handler(int argc, char **argv);
 #endif
 
+#ifdef MODULE_I2C_SCAN
+extern int _i2c_scan(int argc, char **argv);
+#endif
+
 const shell_command_t _shell_command_list[] = {
     {"reboot", "Reboot the node", _reboot_handler},
 #ifdef MODULE_CONFIG
@@ -237,6 +241,9 @@ const shell_command_t _shell_command_list[] = {
 #endif
 #ifdef MODULE_APP_METADATA
     {"app_metadata", "Returns application metadata", _app_metadata_handler },
+#endif
+#ifdef MODULE_I2C_SCAN
+    { "i2c_scan", "Performs an I2C bus scan", _i2c_scan },
 #endif
     {NULL, NULL, NULL}
 };