# Combining Sensors and Recording

We can now combine different sensors to take multiple readings. It would be useful to also save/log multiple readings.

In this section we will cover how

## Combining with SD cards

We will take the code we developed to measure both VOCs and temperature and humidity and record those values to a SD card.

We will assume you have followed the guide on how to wire up a SD card

``` {code-block}
import board
import busio
import sdcardio
import storage
import time
import microcontroller
import digitalio
#Add imports for your sensor(s)

spi = busio.SPI(board.GP2, MOSI = board.GP3, MISO = board.GP4)   #Assign the SPI pins
cs = board.GP0
led = digitalio.DigitalInOut(board.LED)
led.direction = digitalio.Direction.OUTPUT

sdcard = sdcardio.SDCard(spi, cs)   #Create an object for the SD card
vfs = storage.VfsFat(sdcard)        #Create an object for the SD card's filesystem
storage.mount(vfs, "/sd")           #Represent the filesystem with an "sd" folder

filepath = "/sd/temperature.txt"    #Create a variable to hold the filepath

with open(filepath, "a") as f:
    f.write('Starting new set of measurements\n')
    f.write('')
print('Writing to SD card\n')

#Add set up code for your sensors

while True:
    try:
        #Acquire code goes here
        with open(filepath, "a") as f:
            f.write(f"Results: {Results}\n")
            print(f"Results: {Results}\n")
    except OSError as e:
        led.value = False
        time.sleep(0.5)
        led.value = True
        print(e)
    time.sleep(5)
```

Here we have taken the existing SD code and added comments where the sensor codes need to be added

``` {code-block}
import board
import busio
import sdcardio
import storage
import time
import microcontroller
import digitalio

#Add imports for your sensor(s)
import adafruit_dht
import adafruit_sgp30


spi = busio.SPI(board.GP2, MOSI = board.GP3, MISO = board.GP4)   #Assign the SPI pins
cs = board.GP0
led = digitalio.DigitalInOut(board.LED)
led.direction = digitalio.Direction.OUTPUT

sdcard = sdcardio.SDCard(spi, cs)   #Create an object for the SD card
vfs = storage.VfsFat(sdcard)        #Create an object for the SD card's filesystem
storage.mount(vfs, "/sd")           #Represent the filesystem with an "sd" folder

filepath = "/sd/temperature.txt"    #Create a variable to hold the filepath

with open(filepath, "a") as f:
    f.write('Starting new set of measurements\n')
    f.write('')
print('Writing to SD card\n')

#Add set up code for your sensors
# Set up DHT connection
dht = adafruit_dht.DHT11(board.GP0)

#Set up the SPG30 connection
i2c = busio.I2C(board.GP21, board.GP20, frequency=100000)
sgp30 = adafruit_sgp30.Adafruit_SGP30(i2c)

sgp30.iaq_init()

elapsed_sec = 0
while True:
    try:
        # Get the temp and humidity
        temp = dht.temperature
        humidity = dht.humidity
        # Now get the VOC concentration
        eCO2 = sgp30.eCO2
        TVOC = sgp30.TVOC
        with open(filepath, "a") as f:
            #Acquire code goes here
            f.write(f"({TVOC},{temp},{humidity})")
            print(f"({TVOC},{temp},{humidity})")
    except OSError as e:
        led.value = False
        time.sleep(0.5)
        led.value = True
        print(e)
    time.sleep(5)
```