Differences

This shows you the differences between two versions of the page.

Link to this comparison view

--- en:examples:sensor:lidar [2012/05/30 07:42] – raivo.sell
+++ en:examples:sensor:lidar [2020/07/20 09:00] (current) – external edit 127.0.0.1
@@ Line 4: / Line 4: @@
 //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 61: / 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 69: / 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.1338363757.txt.gz · Last modified: 2020/07/20 09:00 (external edit)