Initial Release

i2c/bus_scan/bus_scan.c

@@ -0,0 +1,70 @@
+/**
+ * Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+// Sweep through all 7-bit I2C addresses, to see if any slaves are present on
+// the I2C bus. Print out a table that looks like this:
+//
+// I2C Bus Scan
+//   0  1  2  3  4  5  6  7  8  9  A  B  C  D  E  F
+// 0
+// 1       @
+// 2
+// 3             @
+// 4
+// 5
+// 6
+// 7
+//
+// E.g. if slave addresses 0x12 and 0x34 were acknowledged.
+
+#include <stdio.h>
+#include "pico/stdlib.h"
+#include "hardware/i2c.h"
+
+// I2C reserves some addresses for special purposes. We exclude these from the scan.
+// These are any addresses of the form 000 0xxx or 111 1xxx
+bool reserved_addr(uint8_t addr) {
+    return (addr & 0x78) == 0 || (addr & 0x78) == 0x78;
+}
+
+int main() {
+    // Enable UART so we can print status output
+    stdio_init_all();
+
+    // This example will use I2C0 on GPIO4 (SDA) and GPIO5 (SCL)
+    i2c_init(i2c0, 100 * 1000);
+    gpio_set_function(4, GPIO_FUNC_I2C);
+    gpio_set_function(5, GPIO_FUNC_I2C);
+    gpio_pull_up(4);
+    gpio_pull_up(5);
+
+    printf("\nI2C Bus Scan\n");
+    printf("   0  1  2  3  4  5  6  7  8  9  A  B  C  D  E  F\n");
+
+    for (int addr = 0; addr < (1 << 7); ++addr) {
+        if (addr % 16 == 0) {
+            printf("%02x ", addr);
+        }
+
+        // Perform a 1-byte dummy read from the probe address. If a slave
+        // acknowledges this address, the function returns the number of bytes
+        // transferred. If the address byte is ignored, the function returns
+        // -1.
+
+        // Skip over any reserved addresses.
+        int ret;
+        uint8_t rxdata;
+        if (reserved_addr(addr))
+            ret = PICO_ERROR_GENERIC;
+        else
+            ret = i2c_read_blocking(i2c0, addr, &rxdata, 1, false);
+
+        printf(ret < 0 ? "." : "@");
+        printf(addr % 16 == 15 ? "\n" : "  ");
+    }
+    printf("Done.\n");
+    return 0;
+}