How to fast read and write data to file?

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skylin008
Posts: 53
Joined: Wed Mar 11, 2015 6:21 am

How to fast read and write data to file?

Post by skylin008 » Thu Nov 15, 2018 9:59 am

Hello everyone. I had a pyboard with stm32f405 chip. I want to read data from SPI port and write to flash with file. I found it every slowly as below code.How to solve with it ? Thanks !

Code: Select all

import pyb
import time
from pyb import Timer
from pyb import Pin
from time import sleep_us
from time import sleep_ms
from time import sleep
from machine import Pin
from machine import SPI

import uio

# spi pin
spi_ss   = 'Y5'
spi_sck  = 'Y6'
spi_mosi = 'Y8'
spi_miso = 'Y7'

# switch pin define
switch = pyb.Switch()

# led pin define
red_led    = pyb.LED(1)
green_led  = pyb.LED(2)
orange_led = pyb.LED(3)
blue_led   = pyb.LED(4)

all_leds = (red_led, green_led, orange_led, blue_led)

pcm_sync = Pin('X1', Pin.OUT_PP)
pcm_sync.low()

sleep_ms(10)

def sync_out(timer):	
	pcm_sync.high()
	sleep_us(10)
	pcm_sync.low()

sample_amount = 2048

class SpiControl:

	def __init__(self):
		self.spi = SPI(2, baudrate = 2048000, firstbit = SPI.MSB, polarity = 0, phase = 0)
		self.ss = Pin(spi_ss, Pin.OUT_PP)
		"""
		self.dummybuf = bytearray(1)
		for i in range(1):
			self.dummybuf = 0xff
		"""

	def read(self):
		response = bytearray(1)
		self.ss.low()
		self.spi.read(1)
		self.ss.high()

		return bytes(response)

spic = SpiControl()

data_buffer = [[] for i in range(sample_amount)]


start_flag = 0

while True:
	print("Programme Start!")	
	sleep (1)	
	if switch.value():
		print("Key Pressed!\r\n")
		tim = Timer(2, freq = 8000)
		tim.callback(sync_out)
		start_flag =1

	if (start_flag):

		print("START2!\r\n")	

		if (spic.read())!= 0xff:
			for loop_value in range(sample_amount):
				data = spic.read()
				data_buffer[loop_value] = '{},'.format(data)
				

		with open('pcm.dat', 'wb') as pcm:
			
			for each_data_value in data_buffer:
				pcm.write(each_data_value)

OutoftheBOTS_
Posts: 516
Joined: Mon Nov 20, 2017 10:18 am

Re: How to fast read and write data to file?

Post by OutoftheBOTS_ » Thu Nov 15, 2018 10:33 am

You are doing it in a very slow way.

You are just reading 1 byte at a time then your also writing 1 byte at a time. It takes much longer to start up the read or start up the write then to do the reading or writing.

You should be able to do it all in 1 hit something like this

Code: Select all

spi = SPI(2, baudrate = 2048000, firstbit = SPI.MSB, polarity = 0, phase = 0)
buff = bytearray(sample_amount)
spi.read(buff)
with open('pcm.dat', 'wb') as pcm:
	pcm.write(buff)

skylin008
Posts: 53
Joined: Wed Mar 11, 2015 6:21 am

Re: How to fast read and write data to file?

Post by skylin008 » Fri Nov 16, 2018 1:51 am

@OutoftheBOTS_ Thanks ,I will be try.

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