software/i2c: add i2c_scan command.

litex/soc/software/bios/cmds/cmd_i2c.c

@@ -61,7 +61,7 @@ define_command(i2c_write, i2c_write_handler, "Write over I2C", I2C_CMDS);
 #endif
 
 /**
- * Command "i2crd"
+ * Command "i2c_read"
  *
  * Read I2C slave memory using 7-bit slave address and 8-bit memory address.
  *
@@ -119,3 +119,31 @@ static void i2c_read_handler(int nb_params, char **params)
 }
 define_command(i2c_read, i2c_read_handler, "Read over I2C", I2C_CMDS);
 #endif
+
+
+/**
+ * Command "i2c_scan"
+ *
+ * Scan for available I2C devices
+ *
+ */
+#ifdef CSR_I2C_BASE
+static void i2c_scan_handler(int nb_params, char **params)
+{
+	int slave_addr;
+
+	printf("\n      0 1 2 3 4 5 6 7 8 9 a b c d e f");
+	for (slave_addr = 0; slave_addr < 0x80; slave_addr++) {
+		if (slave_addr % 0x10 == 0) {
+			printf("\n0x%02x  ", (slave_addr/0x10) * 0x10);
+		}
+		if (i2c_poll(slave_addr)) {
+			printf("+ ");
+		} else {
+			printf(". ");
+		}
+	}
+	printf("\n");
+}
+define_command(i2c_scan, i2c_scan_handler, "Scan for I2C slaves", I2C_CMDS);
+#endif

litex/soc/software/include/base/i2c.h

@@ -18,6 +18,7 @@ extern "C" {
 void i2c_reset(void);
 bool i2c_write(unsigned char slave_addr, unsigned char addr, const unsigned char *data, unsigned int len);
 bool i2c_read(unsigned char slave_addr, unsigned char addr, unsigned char *data, unsigned int len, bool send_stop);
+bool i2c_poll(unsigned char slave_addr);
 
 #ifdef __cplusplus
 }

litex/soc/software/libbase/i2c.c

@@ -201,4 +201,18 @@ bool i2c_write(unsigned char slave_addr, unsigned char addr, const unsigned char
 	return true;
 }
 
+/*
+ * Poll I2C slave at given address, return true if it sends an ACK back
+ */
+bool i2c_poll(unsigned char slave_addr)
+{
+    bool result;
+
+    i2c_start();
+    result = i2c_transmit_byte(I2C_ADDR_RD(slave_addr));
+    i2c_stop();
+
+    return result;
+}
+
 #endif /* CSR_I2C_BASE */