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--- en:examples:sensor:lidar [2012/05/22 09:36] – raivo.sell
+++ en:examples:sensor:lidar [2020/07/20 09:00] (current) – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
 ====== Lidar ======
-<note important>Spell check</note>
 //Necessary knowledge: [HW] [[en:hardware:homelab:communication]], [HW] [[en:hardware:homelab:digi]],  [LIB] [[en:software:homelab:library:usart]], [LIB] [[en:software:homelab:library:module:lcd_graphic]], [LIB] [[en:software:homelab:library:module:sensor]]//
+===== Theory =====
-[{{   :en:examples:sensor:lidar3.jpg?220|SICK Laser Rangefinder (LIDAR)}}]
+[{{  :en:examples:sensor:lidar3.jpg?220|SICK Laser Rangefinder (LIDAR)}}]
-===== Theory =====
 LIDAR (Light Detection and Ranging) is an optical remote sensing system which can measure the distance of a target by illuminating it with light. LIDAR technology is being used in Robotics for the perception of the environment as well as object classification. The ability of LIDAR technology to provide 2D elevation maps of the terrain, high precision distance to the ground, and approach velocity can enable safe landing of robotic and manned vehicles with a high degree of precision.
@@ Line 28: / Line 26: @@
 c = f ∙ τ
-where c is the speed of light and f the modulating frequency, and τ the known modulating wavelength.
+where c is the speed of light and f the modulating frequency and τ the known modulating wavelength.
 The total distance D' covered by the emitted light is:
@@ Line 44: / Line 42: @@
 ===== Practice =====
 [{{  :examples:sensor:lidar:lidar_map.jpg?220|Map created by Lidar}}]
-[{{  :en:examples:sensor:connections.png?220|Connection diagram}}]
-In autonomous robotics as well as industrial robotics SICK laser rangers are very widely used. The SICK LMS 200 can easily be interfaced through RS-232 or RS-422, providing distance measurements over a 180 degree area up to 80 meters away. This lidar is based on a time-of-flight measurement principle.
-To make the SICK operational, it must be wired for power and communication. On the back of the SICK there are two  connectors that looks like serial port connectors. The connector with the female end is for power and the connector with the male end is for communications. The power and the serial cable should be wired as shown in the picture. Lidar can be connected with Robotic HomeLab Communication module using one of the RS-232 connectors.
+In autonomous robotics as well as industrial robotics SICK laser rangers are very widely used. The SICK LMS 200 can easily be interfaced through RS-232 or RS-422, providing distance measurements over a 180 degree area up to 80 meters away. This lidar is based on a time-of-flight measurement principle. The example output of one scan measurement result is shown in the picture on the right.
+[{{  :en:examples:sensor:connections.png?220|Connection diagram}}]
+To make the SICK operational, it must be wired for power and communication. On the back of the SICK there are two  connectors that looks like serial port connectors. The connector with the female end is for power and the connector with the male end is for communications. The power and the serial cable should be wired as shown in the picture. Lidar can be connected with Robotic HomeLab Communication module using one of the RS-232 connectors. Power must be taken from external power source and this is not included in Robotic HomLab kit. Required dc power voltage is 24 V.
 The SICK receives commands as streams of bytes through the serial port. When transmitting data, it sends back streams of bytes corresponding to distance measurements at a given angle.
@@ Line 60: / Line 59: @@
 Decimal Form:	        2	0	2	0	32	36	52	8
-After the start string has been successfully sent, Lidar will begin streaming data over RS232. Incoming data from a scan is sent sequentially as the sensor scans through 180°. For example, if the sensor is set to scan 180° with resolution of 0.5°, the first data point sent will correspond to 0°, the next will correspond to 0.5°, the following to 1°, and so on. This means that there is total of 361 data points. Each distance measurement is sent in the form of two bytes. The least signifficant byte is sent first, followed by the most signifficant byte.When operating in metric mode, the unit for the measurements will be milimeters.
+If the start string is successfully sent, Lidar will begin streaming data over RS232. Incoming data from a scan is sent sequentially as the sensor scans through 180°. For example if the sensor is set to scan 180° with resolution of 0.5° the first data point which was sent will correspond to 0°, the next will correspond to 0.5°, the following to 1°, and so on. This means  there is total of 361 data points. Each distance measurement is sent in the form of two bytes. The least signifficant byte is sent first followed by the most signifficant byte. Operating in metric mode the unit for the measurements is in milimeters.
-Finally, to stop the sensor from sending data, a stop string must be sent. This string is:
+Finally to stop the sensor from sending data a stop string must be sent. This string is:
 Hexadecimal Form:	02	00	02	00	20	25	35	08
@@ Line 68: / Line 67: @@
 Decimal Form:	        2	0	2	0	32	37	53	8
-Following example shows how to initiate Lidar and measure the distance.
+Following example shows how to initiate Lidar and get the count of package.
 <code c>
+#include <stdio.h>
+#include <homelab/delay.h>
+#include <homelab/pin.h>
+#include <homelab/module/lcd_gfx.h>
+#include <homelab/usart.h>
-</code>
+// Defining USART interface.
+usart port = USART(0);
+// Defining button pins.
+pin button1 = PIN(C, 0);
+pin button2 = PIN(C, 1);
+// Initialize
+static inline void init()
+{
+	// Setting buttons pins as inputs.
+	pin_setup_input_with_pullup(button1);
+	pin_setup_input_with_pullup(button2);
+	// Set-up of the LCD.
+	lcd_gfx_init();
+ 	// Cleaning the screen.
+	lcd_gfx_clear();
+ 	// Switching on the background light.
+	lcd_gfx_backlight(true);
+ 	// Displaying the name of the program.
+	lcd_gfx_goto_char_xy(3, 1);
+	lcd_gfx_write_string("Lidar");
+	// The set-up of the USART interface.
+	usart_init_async
+	(
+		port,
+		USART_DATABITS_8,
+		USART_STOPBITS_ONE,
+		USART_PARITY_NONE,
+		USART_BAUDRATE_ASYNC(9600)
+	);
+}
+// Main program
+int main(void)
+{
+	unsigned char new_value1, new_value2, old_value1 = 0, old_value2 = 0;
+	char c;
+	int i = 0;
+	int count = 0;
+	char text[16];
+	// Initialize
+	init();
+	// Endless cycle
+	while (1)
+	{
+		// Reads buttons states
+		new_value1 = pin_get_debounced_value(button1);
+		new_value2 = pin_get_debounced_value(button2);
+		// Button S1 is pressed.
+		if((!new_value1) && (old_value1))
+		{
+			//Send "02 00 02 00 20 24 34 08" to start scanning.
+			usart_send_char(port, 0x02);
+			usart_send_char(port, 0x00);
+			usart_send_char(port, 0x02);
+			usart_send_char(port, 0x00);
+			usart_send_char(port, 0x20);
+			usart_send_char(port, 0x24);
+			usart_send_char(port, 0x34);
+			usart_send_char(port, 0x08);
+		}
+		// Button S2 is pressed.
+		if((!new_value2) && (old_value2))
+		{
+			//Send "0x 02 00 02 00	20 25 35 08" to stop scanning.
+			usart_send_char(port, 0x02);
+			usart_send_char(port, 0x00);
+			usart_send_char(port, 0x02);
+			usart_send_char(port, 0x00);
+			usart_send_char(port, 0x20);
+			usart_send_char(port, 0x25);
+			usart_send_char(port, 0x35);
+			usart_send_char(port, 0x08);
+		}
+		// Remembers the last keys values.
+		old_value1 = new_value1;
+		old_value2 = new_value2;
+		// Try to read serial port
+		if (usart_try_read_char(port, &c))
+		{
+			// Find a header "0x 02 81 D6 02 B0 69 41"
+			// Very basic package start search.
+			if(c == 0x02) i++;
+			if(c == 0x81) i++;
+			if(c == 0xD6) i++;
+			if(c == 0x02) i++;
+			if(c == 0xB0) i++;
+			if(c == 0x69) i++;
+			if(c == 0x41) i++;
+			//If there is an header
+			if(i >= 7)
+			{
+				//Increse packet counter
+				count++;
+				//Displaying packet count on the LCD.
+				lcd_gfx_goto_char_xy(0, 3);
+				sprintf(text, "Pakette: %i", count);
+				lcd_gfx_write_string(text);
+				i=0;
+			}
+		}
+	}
+}
+</code>

en/examples/sensor/lidar.1337679417.txt.gz · Last modified: 2020/07/20 09:00 (external edit)