Python-Arduino returns empty string (pyserial)

Question

I have been struggling for the past few days to solve this problem but it end up fails.

I connect serial SRAM to my Arduino and read the SRAM's start-up value which is for example (010101011001....) to make a Physical Unclonable Function.

So, I am trying to use Python to automate my Arduino to read the start-up value of the SRAM and record it into Excel. The Python will send byte H to the serial monitor and once it has been detected, the Arduino will read the start-up value of SRAM.

The problem I face is that Python returns an empty string of start-up value from the serial monitor. The output should be as mentioned above, a stream of random 0 and 1.

When I send H command in the serial monitor, it works fine, but when I try using Python to run it, the Arduino's LED did blink but Python returned an empty string instead of returning stream of 0 and 1.

Any help would be much appreciated.

Arduino code:

#include <SPI.h>

/************SRAM opcodes: commands to the 23LC1024 memory chip ******************/
#define RDMR        5       // Read the Mode Register
#define WRMR        1       // Write to the Mode Register
#define READ        3       // Read command
#define WRITE       2       // Write command
#define RSTIO     0xFF      // Reset memory to SPI mode
#define ByteMode    0x00    // Byte mode (read/write one byte at a time)
#define Sequential  0x40    // Sequential mode (read/write blocks of memory)
#define CS          10      // Chip Select Line for Uno
#define PS          7
#define MI          12
#define SC          13
#define MO          11
#define HO          4
/*******************  Create Global Variables *********************/
byte i = 0;                                   // loop counter variable

/*******  Set up code to define variables and start the SCI and SPI serial interfaces  *****/
void setup(void) {
  int var;
  uint32_t address = 0;                       // create a 32 bit variable to hold the address
  byte value;                                 // create variable to hold the data value read
  byte data;                                  // create variable to hold the data value sent
  pinMode(PS,OUTPUT);
  pinMode(CS,OUTPUT);                        // Make pin 10 of the Arduino an output
  pinMode(HO,OUTPUT);
  Serial.begin(9600);                         // set communication speed for the serial monitor
  SPI.begin();                                // start communicating with the memory chip
  digitalWrite(PS, HIGH);
  digitalWrite(HO, HIGH);    

}
void loop() { // nothing to do in the loop
  /********* Read a single Byte Each Time to Memory *********************/
 int var;
 uint32_t address = 0;                       // create a 32 bit variable to hold the address
 byte value;                                 // create variable to hold the data value read
 byte data;
 if (Serial.available() > 0) {
  
  var = Serial.read();

  if (var == 'H') {
  
  SetMode(ByteMode);                          // set to send/receive single byte of data
  for(i = 0; i <=63; i++) {                   // start at memory location 0 and end at 64
    address = i;                              // use the loop counter as the memory address
    value = ReadByte(address);                // reads a byte of data at that memory location
    for (int j = 0; j < 8; j++) {
        bool b = value & 0x80;
        Serial.print(b);
        value = value << 1;
    }
  }
  //Serial.println();  
  }
 } 
}

/*  Functions to Set the Mode, and Read and Write Data to the Memory Chip ***********/

/*  Set up the memory chip to either single byte or sequence of bytes mode **********/
void SetMode(char Mode) {                       // Select for single or multiple byte transfer
  digitalWrite(CS, LOW);                        // set SPI slave select LOW;
  SPI.transfer(WRMR);                           // command to write to mode register
  SPI.transfer(Mode);                           // set for sequential mode
  digitalWrite(CS, HIGH);                       // release chip select to finish command
}

/************ Byte transfer functions ***************************/
byte ReadByte(uint32_t address) {
  char read_byte;
  digitalWrite(CS, LOW);                         // set SPI slave select LOW;
  SPI.transfer(READ);                            // send READ command to memory chip
  SPI.transfer((byte)(address >> 16));           // send high byte of address
  SPI.transfer((byte)(address >> 8));            // send middle byte of address
  SPI.transfer((byte)address);                   // send low byte of address
  read_byte = SPI.transfer(0x00);                // read the byte at that address
  digitalWrite(CS, HIGH);                        // set SPI slave select HIGH;
  return read_byte;                              // send data back to the calling function
}

Python code:

import serial
import time
import openpyxl, math
from openpyxl import Workbook, load_workbook

data_file='SRAM_TEST.xlsx'
wb = load_workbook(filename= data_file)
sheet_data = wb['Sheet1']

for x in range(1,3):
    with serial.Serial('COM4', 9600, timeout=1) as ser:
        time.sleep(0.5)
        ser.write(b'H')
        data=ser.read(size=1)
        data1=data.decode()
        sheet_data.cell(row=x, column=1).value=data1
        print(data1)

Solution: change the with serial.Serial('COM4', 9600, timeout=1) as ser: to this solve the problem.

if (Serial.available() > 0){

  var = Serial.read();

  if (var == 'H'){

question from:https://stackoverflow.com/questions/65559820/python-arduino-returns-empty-string-pyserial

Answer 1

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