ESP32 SPI data send to RaspberryPi4

ESP32_SPI_slave_to_RPi4.ino

/*; PlatformIO Project Configuration File
;
;   Build options: build flags, source filter
;   Upload options: custom upload port, speed and extra flags
;   Library options: dependencies, extra library storages
;   Advanced options: extra scripting
;
; Please visit documentation for the other options and examples
; https://docs.platformio.org/page/projectconf.html

[env:esp32doit-devkit-v1]
platform = espressif32
board = esp32doit-devkit-v1
framework = arduino
upload_port = COM9
monitor_port = COM9
monitor_speed = 115200
lib_deps = hideakitai/ESP32DMASPI@^0.3.0
*/
#include <Arduino.h>
#include <ESP32DMASPISlave.h>

ESP32DMASPI::Slave slave;

// HallSensor Analog value is connected to GPIO 35 (Analog ADC1_CH7)
const int hallSensorPin = 35;
const int hallSensorDPin = 13;

int i = 0;
static const uint32_t BUFFER_SIZE = 8;
uint8_t *spi_slave_tx_buf;
uint8_t *spi_slave_rx_buf;

void set_buffer()
{
  for (uint32_t i = 0; i < BUFFER_SIZE; i++)
  {
    spi_slave_tx_buf[i] = i+ 0x31;
  }
  //memset(spi_slave_rx_buf, 0, BUFFER_SIZE);
}

void setup()
{
  Serial.begin(115200);

  // to use DMA buffer, use these methods to allocate buffer
  spi_slave_tx_buf = slave.allocDMABuffer(BUFFER_SIZE);
  spi_slave_rx_buf = slave.allocDMABuffer(BUFFER_SIZE);

  set_buffer();
  delay(5000);

  // slave device configuration
  slave.setDataMode(SPI_MODE0);
  slave.setMaxTransferSize(BUFFER_SIZE);

  // begin() after setting
  slave.begin(VSPI); // HSPI = CS: 15, CLK: 14, MOSI: 13, MISO: 12 -> default
                     // VSPI (CS:  5, CLK: 18, MOSI: 23, MISO: 19)
  pinMode(hallSensorDPin, INPUT);
  Serial.println("Boot finalized!");
}

void loop()
{
  i=i+4;
  uint8_t hallSensorDValue = digitalRead(hallSensorDPin);
  uint16_t HallSensorValue = analogRead(hallSensorPin);
  Serial.print("Analog Data: ");
  Serial.println(HallSensorValue);
  uint8_t val_hall = map(HallSensorValue, 0,4095, 0, 255);
  if(i==7)
    i = 0;
 
  spi_slave_tx_buf[0] = val_hall;
  spi_slave_tx_buf[1] = 0xff;
  
  // if there is no transaction in queue, add transaction
  if (slave.remained() == 0)
  {
    slave.queue(spi_slave_rx_buf, spi_slave_tx_buf, BUFFER_SIZE);
  }

  // if transaction has completed from master,
  // available() returns size of results of transaction,
  // and buffer is automatically updated

  while (slave.available())
  {
    //Serial.printf("Slave received: %s\n\r", spi_slave_rx_buf);
    //Serial.printf("Slave Transmitted: %s\n\r", spi_slave_tx_buf);
    slave.pop();
  }
  delay(50);
}