Raspberry Pi 3 fast boot img ready - Run Python app piSerial ttyS0 fast

Hi Furkan, I am a big fan of raspberry pi and Python I have developed many scripts in Python Serial ttyX to extract data registers from controllers.

Now for a critical application I would need my Python serial application active in a few seconds, unfortunately even with raspberry pi 4 it takes an average of 5-7 seconds to initialize my script (I use the systemd linux daemon to activate my scripts).

I have to read from the serial and give immediate printing instructions on an ESC-POS label printer device, in a maximum of 2 seconds from power on my program must already be running on the raspberry.

Now I downloaded your fastboot raspberry image in 2 seconds, I wanted to ask you if you can use my scripts already, Python 3.7 is installed, can my python 3.7 script be run?

They tell me that ESP type microcontrollers are much faster to boot but I would like to stay on a fast raspberry linux board.

thanks for now Rocco

Hey Rocco,

Now I downloaded your fastboot raspberry image in 2 seconds, I wanted to ask you if you can use my scripts already, Python 3.7 is installed, can my python 3.7 script be run?

If there is no graphical application to run, the current work hits 1.25sec from power-up to Linux userspace with serial connection enabled, by using start_cd.elf.

In your use-case, Python interpreter initialization and your Python script initialization will be run after Linux is ready. To run Python script, we can have different strategies. The first thing comes my mind is as the following;

I would statically cross compile CPython for the target device and try to embed my script in it. Maybe even you can directly convert your Python script to executable file, this could be easier but less flexible. After that I would have a single file of statically compiled CPython and my script is embedded in it.

(0.75sec) Hardware boot (start_cd.elf is used)
(0.25sec) Linux pre-boot
(0.25sec) Linux boot (till here, you can use ftdev_rpi3)
Statically compiled file (just put it to /sbin/init). If you need to initialize anything, you need to do it manually in statically compiled file at this point. I don't really know how much time this part will take.

They tell me that ESP type microcontrollers are much faster to boot but I would like to stay on a fast raspberry linux board.

This totally depends on your constrains like development time, cost, developer, usecase... You can even use FPGA for that but does this make sense ? So just you decide what you really want to do. If I were you, I would not use Python for this job, I have lots of good reasons for that but this is just me.

thanks for now

It's fun to work on this. Good job. Don't hesitate to contact!

Regards, Furkan

Hello Furkan, my Python MODBUS script is already be executable, command sudo python3 myScript.py

The script is now automatically executed at startup by the powerful Systemd LINUX daemon!

Now I'm sorry I didn't quite understand what well what you mean with Cpython (I know python not cpython), embed a script in it what does it mean?

What should I incorporate, remember that it is the raspberry machine (MASTER) that simply executes the PYTHON script, not the MODBUS (SLAVE) card which is instead interrogated.

I have now written your rasbian image on the microsd, could you kindly describe me the steps to start the raspberry machine from ssh terminal. I would like to start testing it on the raspberry machine via ssh terminal: 1) can i start raspberry from ssh? I remember that I program the raspberry from the ssh terminal after configuring the wlan0 of the linux machine (etc / network / interfaces) 2) where do I configure wlan0 for the first boot ssh access via terminal? 3) Is Python 3.7 already installed in your raspberry image? if you can't install with pip?

If I can get the Python Serial application to go fast start with your special rom I would like to stay so long on the raspberry machine, esp8266 I don't know it.

I am attaching the minilmodbus python script (powerful Python libraries) which reads and writes the registers on the modbus slave board.

thanks for now Rocco

Script Python MODBUS:

import minimalmodbus import time import threading import subprocess import logging import serial import socket import fcntl import struct

instrument = minimalmodbus.Instrument("/dev/ttyS0", 1) # port slave address , 1=ID SLAVE instrument.serial.baudrate = 4800 # Baud instrument.serial.bytesize = 8

instrument.serial.parity = PARITY_NONE

instrument.serial.stopbits = 1 instrument.serial.timeout = 0.50 # seconds instrument.debug = False #Da testare "True" in caso di errore IOError Communication

while True: try:

    ## Read temperatura registro 102 ----> signed=True
    t1 = instrument.read_register(102,0,3,signed=True) 
    print "t1=",str(t1)
    time.sleep(0.01)

    ## Read temperatura registro 103 ----> signed=True
    t2 = instrument.read_register(103,0,3,signed=True)
    print "t2=",str(t2)
    time.sleep(0.01)

    ## Read version software ---> intero ----> signed=False
    versionSoft= instrument.read_register(136,0,3,signed=False) 
    print "versionSoft=",str(versionSoft)
    time.sleep(0.01)

    ## Read ai[A/ora] istantanei con Decimals=1 --->  signed=False
    ai = instrument.read_register(108,1,3,signed=False) 
    print "ai=",str(ai)
    time.sleep(0.01)

    ## Read ah[Kwh]=32bit=16bit_hight+16bit_low ---> signed=False
    ah = instrument.read_long(110,3,signed=False)
    print "ah=",str(ah)
    time.sleep(0.01)

    ## Read h1 long 32 bit
    h1= instrument.read_long(128,3,signed=False)
    print "h1=",str(h1)
    time.sleep(0.01)

    ## Read h2 long 32 bit=
    h2 = instrument.read_long(130,3,signed=False)
    print "h2=" ,str(h2)
    time.sleep(0.01)

    ## Read h3=2 registri da 16 bit
    h3 = instrument.read_long(132,3,signed=False)
    print "h3=",str(h3)
    time.sleep(0.01)

    ## Read h4=2 registri da 16 bit=32bit=16bit_hight+16bit_low
    h4 = instrument.read_long(134,3,signed=False)
    print "h4=" ,str(h4)
    time.sleep(0.01)

    ## Read t1_max
    t1_max = instrument.read_register(104,0,3,signed=True)
    print "t1_max=",str(t1_max)
    time.sleep(0.01)

    ## Read t1_min
    t1_min = instrument.read_register(105,0,3,signed=True)
    print "t1_min=",str(t1_min)
    time.sleep(0.01)

    ##Read t2_max
    t2_max = instrument.read_register(106,0,3,signed=True)
    print "t2_max=",str(t2_max)
    time.sleep(0.01)

    ## Read stato dig. 1 (Function INVERSIONE stato digitale)
    i1 = int(not instrument.read_register(127,0,3,signed=False))
    time.sleep(0.01)
    print "i1=",i1

    ## Read stato digitale 2
    i2 = int(not instrument.read_register(126,0,3,signed=False))
    time.sleep(0.01)
    print "i2=",i2

    ## Read stato digitale 3
    i3 = int(not instrument.read_register(125,0,3,signed=False))
    time.sleep(0.01)
    print "i3=",i3

    ## Read stato digitale 4
    i4 = int(not instrument.read_register(124,0,3,signed=False))
    time.sleep(0.01)
    print "i4=",i4

    ## Read stato digitale 5
    i5 = int(not instrument.read_register(123,0,3,signed=False))
    time.sleep(0.01)
    print "i5=",i5

    ## **************WRITE_REGISTER_MODBUS **********************
    ## write registro 16 bit e lettura
    # t1max=30
    # instrument.write_register(104, t1max,0,16,signed=False) 
    # t1max_write = instrument.read_register(104, 0,3,signed=True) 
    # print "t1max_write=",str(t1max_write)
    # time.sleep(0.15)

    ## write registro 32 bit e lettura
    # impulsi2=450000
    # instrument.write_long(114, impulsi2,signed=False) 
    # impulsi2_write = instrument.read_long(114,3,signed=False) 
    # print "impulsi2_write",str(impulsi2_write)
    # time.sleep(0.15)

    ##WRITE ser[long]=32bit=16bit_hight+16bit_low
    #ser_w=120
    #instrument.write_long(100,ser_w,signed=False)
    #ser_w = instrument.read_long(100,3,signed=False)
    #print "ser_w=",str(ser_w)
    #time.sleep(0.15)

    print '*' * 100 + "\n"

## Capture Exception IOError
except IOError:
    print IOError

## Capture Exception ValueError
except  ValueError:
    print ValueError

The script is now automatically executed at startup by the powerful Systemd LINUX daemon!

In fastboot, you need control and minimalism so big projects like systemd is bad for fastboot. There are fits-better-to-fastboot-application init systems. More of that, I recommend you to cancel init system at all, if you can.

Now I'm sorry I didn't quite understand what well what you mean with Cpython (I know python not cpython), embed a script in it what does it mean?

Its the source code of the Python interpreter. Check it online for details.

I have now written your rasbian image on the microsd, could you kindly describe me the steps to start the raspberry machine from ssh terminal.

If you don't have to use ssh, use serial connection: https://www.instructables.com/How-to-Access-Headless-Raspberry-Pi-Using-USB-to-T/

can i start raspberry from ssh? I remember that I program the raspberry from the ssh terminal after configuring the wlan0 of the linux machine (etc / network / interfaces)

There are several strategies for that. You can search about this by the following keywords: raspberry network boot

where do I configure wlan0 for the first boot ssh access via terminal?

This is not really related with fastboot. It depends on your userspace network manager. For example, I use the following settings for a system with systemd and connman

Copy the following 2 files into the /var/lib/connman;

connman-settings.config

[global]
OfflineMode=false

[Wired]
Enable=true
Tethering=false

[WiFi]
Enable=true
Tethering=false

connection-settings.config

# Your wifi info
[service_ftwifi]
Type = wifi
Name = yourwifiname
Passphrase = yourwifipassword
IPv4 = dhcp

I wrote a script that checks usb wifi and reset it if the connection is broken;

ftwifi

#!/usr/bin/python3

import time
import threading
import utils as u

class FtWifi(object):
        def __init__(self):
                self.adapter_port = "1-1.3"

                self.thread = threading.Thread(target=self.loop)
                self.__is_running = False

        def plug_adapter(self):
                u.run_cmd("echo " + self.adapter_port + " > /sys/bus/usb/drivers/usb/bind")

        def unplug_adapter(self):
                u.run_cmd("echo " + self.adapter_port + " > /sys/bus/usb/drivers/usb/unbind")

        def replug_adaptor(self):
                self.unplug_adapter()
                time.sleep(3)
                self.plug_adapter()
                time.sleep(3)

        ###
        ### Run functions
        ###
        def loop(self, is_threaded=True):
                self.__is_running = not is_threaded
                sleep_time = 10
                while self.__is_running:
                        self.run()
                        time.sleep(sleep_time)

        # Return True if online, False if offline.
        def run(self):
                is_connected = u.is_connected("wlan0")
                if not is_connected: is_connected = u.is_connected("eth0")

                if not is_connected:
                        u.log("Disconnected. Repluging the adapter.")
                        self.replug_adaptor()

                return is_connected

        def start(self):
                if self.__is_running: return

                self.__is_running = True
                self.thread.start()

        def stop(self):
                self.__is_running = False

if __name__ == "__main__":
        app = FtWifi()
        app.loop(is_threaded=False)

I have a systemd service that runs the script above;

ftwifi.service

[Unit]
Description=FT USB wifi handler.

[Service]
Type=oneshot
RemainAfterExit=yes                             
ExecStart=/bin/ftwifi

[Install]            
WantedBy=basic.target

This was working on iMX6. It was okay for my usecase, you should create your own solution that fits to your own usecase.

Is Python 3.7 already installed in your raspberry image? if you can't install with pip?

No but you can install whatever you want by your own. This is a base image.

To sum up, what you're doing requires a plan and time. Please also read my previous message by checking the terms online. Hope that you can handle it! You can update your status here to let us know the progress.

Hi Furkan, I don't understand well, systemd can be used on your fast rom? Is present?

I would simply like to understand the quick steps to use your quick rom on the raspberry and run the Python script with systemd or other system.

if you can better specify the steps for your rom run thanks for now R

Il giorno ven 4 dic 2020 alle ore 17:17 Furkan Tokaç < notifications@github.com> ha scritto:

Closed #7 https://github.com/furkantokac/buildroot/issues/7.

— You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub https://github.com/furkantokac/buildroot/issues/7#event-4073428365, or unsubscribe https://github.com/notifications/unsubscribe-auth/APR4KIDICYUM6CTS2JEWN7TSTEDSHANCNFSM4SUK65JQ .

furkantokac / buildroot

Raspberry Pi 3 fast boot img ready - Run Python app piSerial ttyS0 fast #7

instrument.serial.parity = PARITY_NONE