GlobalLogic BaseCamp final project

1. mpu6050 gyroscope

1.1 The project uses the GY-521 gyroscope module.

Output AD0 - connected to a power source, in this configuration the gyroscope  
has an i2c address of 0x69.  
(Some GY-521 module with a RED power LED have a DEVICE ID of 0x98).  

1.2 File gl_mpu6050-overlay.dts - modified with address 0x69 and driver name gl_mpu6050.

For compile gl_mpu6050.dts to .dtbo - use make dtb.  
For correct operation, the file gl_mpu6050.dtbo must be located in  
the raspberry pi /boot/overlays.  
To enable the overlay in the system, add dtoverlay=gl_mpu6050 to config.txt.  

1.3 Implemented sysfs, read only.

Raw accelerometer data is stored in the /sys/devices/mpu6050/accel/accel_x,  
.../accel_y or .../accel_z.     
Raw gyroscope data is stored in the /sys/devices/mpu6050/gyro/gyro_x,     
.../gyro_y or .../gyro_z.     
Temperature data is stored in the /sys/devices/mpu6050/temp - in degrees     
Celsius.     

1.4 Add simply motion detector.

Movement is tracked by two coordinates (x, y).     
We use a simple method to determine the direction, it is based on the     
position of the accelerometer. These coordinates are in the range  
from 0 to +/- 16340, the sensitivity threshold for an example,  
let's choose 8000. If the sensitivity threshold is exceeded, we register  
the direction left, right, forward, backward.  
/sys/devices/mpu6050/direct - is used to export data to user space  
2 - moving forward,  
8 - back,  
4 - left,  
6 - right,  
0 - no moving.  

2. 4x4 matrix keyboard

2.1 Initialization the gpio's column (output) and row (input) for keyboard.

A simple test was used by turning on the LED when the module was loading  
and turning it off after exiting the module.  

2.2 Timer added.

An LED is used for testing, the ON/OFF period is 100ms.  

2.3 Keypad connection:

Keypad pinout:  1 <-> ROW3    (GPIO16) Raspberry pi.  
                2 <-> ROW2    (GPIO25)  
                3 <-> ROW1    (GPIO24)  
                4 <-> ROW0    (GPIO23)  
                5 <-> COL3    (GPIO 5)  
                6 <-> COL2    (GPIO22)  
                7 <-> COL1    (GPIO27)  
                8 <-> COL0    (GPIO17)  
The keyboard is polled every 100 ms.  
The algorithm does not track long presses or presses of several keys  
at the same time.  
Reading from /dev/gl_keyb returns only direction commands:  
2 - forward,  
8 - back,  
4 - left,  
6 - right.  

3. ITDB02-1.8SP (ST7735) display 160x128 65k colors

3.1 To connect the display, we use the driver from the Linux kernel.

 Add to /boot/config.txt  
 dtoverlay=adafruit-st7735r,160x128,reset_pin=21,dc_pin=20  
 pinouts:  
             CS      <->     SPI0 CE0        (GPIO8)    
             SCL     <->     SPI0 CLK        (GPIO11)   
             SDA     <->     SPIO MOSI       (GPIO10)   
             RS      <->     DATA/COMD       (GPIO20)   
             RST     <->     RESET           (GPIO21)   
             GND  
             +5V/+3.3V  
To work with the display, we use the frame buffer and memory mapping.  

4. User space (main.c)

This is a simple program to demonstrate the operation of Linux kernel  
drivers - display, gyroscope and matrix keyboard.  
We get the direction of movement from the gyroscope and the 4x4 matrix  
keyboard. By direction - we move the "head" on the display.  
TODO: implement the snake game.