7. Touchscreen Experiment

Routine Code

import touchscreen as ts
from machine import I2C
import lcd, image
from board import board_info
from fpioa_manager import fm
from maix import GPIO

fm.register(board_info.BOOT_KEY, fm.fpioa.GPIO1, force=True)
btn_clear = GPIO(GPIO.GPIO1, GPIO.IN)

lcd.init()                                             
i2c = I2C(I2C.I2C0, freq=400000, scl=24, sda=25)        
ts.init(i2c)                                            
#ts.calibrate()                                         
lcd.clear()                                            
img = image.Image()
status_last = ts.STATUS_IDLE
x_last = 0
y_last = 0
draw = False

while True:
    (status,x,y) = ts.read()
    print(status, x, y)
    if draw:
        img.draw_line((x_last, y_last, x, y))
    if status_last!=status:
        if (status==ts.STATUS_PRESS or status == ts.STATUS_MOVE):
            draw = True
        else:
            draw = False
        status_last = status
    lcd.display(img)
    x_last = x
    y_last = y
    if btn_clear.value() == 0:
        img.clear()

Experiment Preparation

1. Connect the K210 to your computer via USB.
1. Open CanMV IDE and run the routine code above.

Experiment Results

1. After running, the K210 continuously processes touchscreen input and draws touch trajectories on the LCD. A white line follows the touch path, and touch coordinates are printed in the Serial Terminal until the BOOT button is pressed to clear the screen.

Routine Code Explanation

1. Import the modules required to run the routine. The touchscreen module (alias ts) handles touchscreen operations. I2C configures I2C communication. lcd and image handle LCD display and image operations. board_info, fpioa_manager (alias fm), and maix.GPIO handle board pin configuration, function mapping, and GPIO operations.

import touchscreen as ts
from machine import I2C
import lcd, image
from board import board_info
from fpioa_manager import fm
from maix import GPIO

1. Use fm.register to configure the board's BOOT_KEY pin as GPIO1 with forced registration. Create GPIO object btn_clear as input to detect when the button is pressed to clear the screen image.

fm.register(board_info.BOOT_KEY, fm.fpioa.GPIO1, force=True)
btn_clear = GPIO(GPIO.GPIO1, GPIO.IN)

1. Initialize the LCD. Configure I2C object i2c on I2C0 at 400000 Hz with SCL on pin 24 and SDA on pin 25. Initialize the touchscreen on this I2C bus for communication.

lcd.init()                                              
i2c = I2C(I2C.I2C0, freq=400000, scl=24, sda=25)        
ts.init(i2c)

1. ts.calibrate() is commented out; calibration is not needed for now. Clear the LCD for drawing. Create image.Image object img. Initialize variables: status_last to idle (ts.STATUS_IDLE), x_last and y_last to 0 for previous touch coordinates, and draw to False to control drawing.

#ts.calibrate()                                         # Touchscreen calibration
lcd.clear()                                             # Clear screen
img = image.Image()
status_last = ts.STATUS_IDLE
x_last = 0
y_last = 0
draw = False

1. Enter an infinite loop.

while True:

1. Read touchscreen status and current touch coordinates, then print them.

(status, x, y) = ts.read()
print(status, x, y)

1. If draw is True, draw a line from the previous touch point (x_last, y_last) to the current point (x, y) to record the touch trajectory.

if draw:
    img.draw_line((x_last, y_last, x, y))

1. When the touchscreen status changes from the previous state: if the current state is press or move, set draw to True to start or continue drawing; otherwise set draw to False to stop (e.g., when the finger is lifted). Update status_last to the current status.

if status_last!= status:
    if (status == ts.STATUS_PRESS or status == ts.STATUS_MOVE):
        draw = True
    else:
        draw = False
    status_last = status

1. Display the image with touch trajectories on the LCD.

lcd.display(img)

1. Update the previous touch coordinates to the current coordinates for the next line segment.

x_last = x
y_last = y

1. If draw is True, draw a line from (x_last, y_last) to (x, y) on img to record the touch trajectory.

if draw:
    img.draw_line((x_last, y_last, x, y))

1. Check if the clear button is pressed. If pressed (btn_clear.value() == 0), clear img to restart drawing.

if btn_clear.value() == 0:
    img.clear()