[bowei zhang]

#2443

This project is implemented by using Raspberry Pi Pico under Thonny compiler with MicroPython language

The work that needs to be prepared before the start of the project is as follows:

hardware:

1. A Raspberry Pi pico board (from:https://www.raspberrypi.org/products/raspberry-pi-pico/)

2. 28byj-48 stepper motor one (from: https://components101.com/motors/28byj-48-stepper-motor)

3. A stepping motor drive circuit

4. A serial port HMI display (Customized Arduino 7-inch display)

5. Several connecting lines

Compile and debug software: Thonny 3.3.5

[bowei zhang]

#2445

Now that the above conditions are ready, let’s start the experiment:

Before connecting, we need to flash the firmware for Pico. The method is to press and hold the bootsel button on the Pico board to connect to the computer through the USB port. At this time, the Pico will be recognized as a removable hard disk. After opening, there are two File, one of which is the official website link, we click on it

[bowei zhang]

#2446

Then find the Download UF2 file to download the MicroPython firmware, after downloading it, copy it to the mobile hard disk RPI-RP2, Pico will automatically restart and the mobile hard disk will pop up, which means that the firmware has been successfully flashed, and it is best to reconnect at this time USB cable.

[bowei zhang]

#2447

Below we determine the connection of each part according to Pico’s pin diagram:

I use a five-wire four-phase motor, so I need to connect four gpio lines to the Pico. Here I choose IN1, IN2, IN3, and IN4 of the drive circuit to correspond to GP9, GP10, GP11, and GP12 on the Pico. , And then the drive circuit also needs a voltage of 5-12V, so here I use the VBUS on the Pico board to provide it with a 5v voltage, and then connect the negative pole of the drive circuit to the GND of the Pico, then this part of the connection is finished.

The following is the connection to the serial screen. There are four sets of UART provided on the Pico board. Choose one of them for connection. Connect the serial screen. The TXP of the serial screen is connected to the RX of the Pico, the RXP of the serial screen is connected to the TX of Pico, and the GND is connected to GND.

[bowei zhang]

#2448

Actual connection：

 

 

 

[bowei zhang]

#2449

Then there is the software debugging part:

Open Thonny and select Raspberry Pi Pico in the lower right corner. When the shell command window prompts as follows, it means that Thonny and Pico are successfully connected:

[bowei zhang]

#2450

When the following prompt appears, it usually means that Pico is running a program. You can press Ctrl+C to interrupt the program according to the prompt.

[bowei zhang]

#2451

Finally, attach the program code：

from machine import UART,Pin
import time

#Define the serial port
uart1 = UART(1, baudrate = 115200, tx = Pin(4), rx = Pin(5))

#Define five-wire four-phase motor pins
motor1a = Pin(9,Pin.OUT)
motor1b = Pin(10,Pin.OUT)
motor1c = Pin(11,Pin.OUT)
motor1d = Pin(12,Pin.OUT)

def forward(delay, maxspeed): #Stepper motor forward function, define stepper motor as double four-shot drive mode
for i in range(0, maxspeed):
motor1a.high()
motor1b.high()
motor1c.low()
motor1d.low()
time.sleep(delay)
motor1a.low()
motor1b.high()
motor1c.high()
motor1d.low()
time.sleep(delay)
motor1a.low()
motor1b.low()
motor1c.high()
motor1d.high()
time.sleep(delay)
motor1a.high()
motor1b.low()
motor1c.low()
motor1d.high()
time.sleep(delay)

def backward(delay, maxspeed): #Stepper motor reversal function
for i in range(0, maxspeed):
motor1a.low()
motor1b.low()
motor1c.high()
motor1d.high()
time.sleep(delay)
motor1a.low()
motor1b.high()
motor1c.high()
motor1d.low()
time.sleep(delay)
motor1a.high()
motor1b.high()
motor1c.low()
motor1d.low()
time.sleep(delay)
motor1a.high()
motor1b.low()
motor1c.low()
motor1d.high()
time.sleep(delay)

def stop(): #Motor stop function
motor1a.low()
motor1b.low()
motor1c.low()
motor1d.low()

def dianji():
forward(0.005, 512)
stop()
time.sleep(3)
backward(0.005, 512)
stop()
time.sleep(3)

def zrun():
forward(0.005, 512)

def frun():
backward(0.005, 512)

#counti = 0
#list2 = []
motor_off = [‘S’, ‘T’, ‘<‘, ‘\x10’, ‘\x10’, ‘\x00’, ‘\x07’, ‘s’, ‘w’, ‘i’, ‘t’, ‘c’, ‘h’, ‘\x00’, ‘>’, ‘E’, ‘T’]#Serial screen command, you can modify it by yourself
motor_on = [‘S’, ‘T’, ‘<‘, ‘\x10’, ‘\x10’, ‘\x00’, ‘\x07’, ‘s’, ‘w’, ‘i’, ‘t’, ‘c’, ‘h’, ‘\x01’, ‘>’, ‘E’, ‘T’]
time.sleep(1)

while True:
counti = 0
list2 = []
try:
rxdata = uart1.read(40)
list1 = list(rxdata)
except BaseException as e:
print(‘串口没有接收到数据’)
time.sleep(3)
else:
#list1 = list(jieshou)
for item in list1:
list2.append(chr(item))
counti += 1
if item == 62: #The serial port returns the decimal value of the ASCII code of the end sign’>’ in the command data
for item2 in range(2): #When the’>’ is read, two characters will be read later to display the complete command, but there are actually two check digit                                                    #characters behind
counts = list1[counti]
list2.append(chr(counts))
counti += 1
break

print(list2)
if list2 == motor_on:
zrun()
elif list2 == motor_off:
stop()
uart1.sendbreak()

[bowei zhang]

#2452

[bowei zhang]

#2456

The program demonstration effect is: when the swtich on the screen is pressed to open, the motor rotates forward, and when it is pressed to close, the motor rotates backward, which can be modified as needed.

[bowei zhang]

#2457

Another point to note is that the above process is debugged and run in the Thonny environment. If you want to download the program to the pico board, just use the save button of Thonny to rename the python file to main.py and save it in the internal space of pico. That’s it

[bowei zhang]

#2458

In the next chapter, I will introduce a project demonstration that uses pico’s dual-threaded parallel and asynchronous processing tasks.

[Clay Grady]

#2469

hello,

Maybe it’s a simple question, but I’d like to ask what does the try except do?

[bowei zhang]

#2470

‘try except else’ is a fixed usage, to judge whether there is data in the buffer, if it is not added, an error will be reported, because uart received None at the beginning of the serial port

[Clay Grady]

#2473

Thank you very much, I get it.

[前史蒂夫·威尔金森]

#2471

Hi,

I tried your program, the program works in the compiler, but when pico executes the program alone, it doesn’t work.

Can you tell me why?

[bowei zhang]

#2472

I have encountered this situation many times, usually because your grammar has logical problems, you can try to check and modify the grammar, or provide your code, I will help you to see

[retnavair]

#2474

Hi，

Why it doesn’t work with uart. readline()?

[Author]

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