![\"Analog-to](\"https:\/\/blog.seeedstudio.com\/wp-content\/uploads\/2020\/10\/Analog-to-Digital-Converter-ADC_-Reading-Raspberry-Pi-Analog-1030x579.png\")
<\/figure><\/div>\n\n\n\nTherefore, in this article, we will be talking about Analog-to-Digital Converters (ADC) and hopefully, this would aid you in your projects!<\/p>\n\n\n\n
What will be covered:<\/p>\n\n\n\n
- Overview of Raspberry Pi Analog-to-Digital Converters (ADC)<\/li>
- Recommendations for Raspberry Pi ADC <\/li>
- Setting up Raspberry Pi ADC<\/li>
- Projects with Raspberry ADC<\/li><\/ul>\n\n\n\n
\n\n\n\nOverview of Raspberry Pi Analog-to-Digital Converters (ADC)<\/h2>\n\n\n\n
What are ADCs?<\/h3>\n\n\n\n
ADCs work to convert analog (continuous, infinitely variable) signals to digital (discrete-time, discrete-amplitude) signals.<\/em><\/p>\n\n\n\n
ADCs are an abbreviation for Analog-to-Digital Converters, they basically convert an analog input into a digital input.<\/p>\n\n\n\n
![\"\"](\"https:\/\/www.rs-online.com\/designspark\/rel-assets\/dsauto\/temp\/uploaded\/header1.png?w=1042\")
Ref: DesignSpark<\/a><\/figcaption><\/figure><\/div>\n\n\n\n If you’re interested to find out more about Analog and Digital signals, click here<\/a>!<\/p>\n\n\n\n
<\/div>\n\n\n\nHow do ADCs work?<\/h3>\n\n\n\n
To understand the concept behind ADCs, need to first know that ADCs follow a sequence when converting analog signals to digital. <\/p>\n\n\n\n
There are 2 features to note about ADCs:<\/p>\n\n\n\n
Sampling Rate (Frequency)<\/h4>\n\n\n\n
- Tied to the ADC\u2019s speed.<\/li>
- Depends on the type of converter and the needed accuracy<\/li>
- Measured by samples per second.<\/li><\/ul>\n\n\n\n
![\"\"](\"https:\/\/static4.arrow.com\/-\/media\/arrow\/images\/miscellaneous\/0\/0418_aliasing_example.jpg?h=307&w=590&la=en&hash=C789B35B99E475FCD9CD32BF3D79A497AF0D2748\")
Ref: Arrow<\/a><\/figcaption><\/figure><\/div>\n\n\n\n The equation for sampling rate is:<\/p>\n\n\n\n
fs<\/sub> = 1\/T<\/em> <\/p>\n\n\n\n
Where,<\/p>\n\n\n\n
fs<\/sub> = Sample Rate\/Frequency<\/p>\n\n\n\n
T = Period of the sample or the time it takes before sampling again.<\/p>\n\n\n\n
<\/div>\n\n\n\nResolution<\/h4>\n\n\n\n
- Determined by its bit length.<\/li>
- The resolution depends on both the bit length and the reference voltage.<\/li><\/ul>\n\n\n\n
![\"\"](\"https:\/\/static4.arrow.com\/-\/media\/arrow\/images\/miscellaneous\/0\/0418_resolution_example.jpg?h=279&w=466&la=en&hash=ED63A8162674BEAE8CF586D3534562F665AF2786\")
Ref: Arrow<\/a><\/figcaption><\/figure><\/div>\n\n\n\n The equation for total resolution is:<\/p>\n\n\n\n
Step Size = VRef<\/sub>\/N<\/em> <\/p>\n\n\n\n
Where, <\/p>\n\n\n\n
Step Size = The resolution of each level in terms of voltage<\/p>\n\n\n\n
VRef<\/sub> = The voltage reference (range of voltages)<\/p>\n\n\n\n
N = Total level size of ADC.<\/p>\n\n\n\n
<\/div>\n\n\n\nWhy are ADCs necessary?<\/h3>\n\n\n\n
As mentioned at the start, Raspberry Pi is not capable of reading analog inputs. Thus, ADCs come in handy to convert analog inputs to outputs, which would help the Pi to be analog-friendly.<\/p>\n\n\n\n
Interested to get a Raspberry Pi ADC now? Read on as we show you some options that Seeed offers!<\/p>\n\n\n\n
\n\n\n\nRecommendations for Raspberry Pi ADC<\/h2>\n\n\n\n
After going through some background of ACD, we will now show you the ADCs that’s compatible with Raspberry Pi! Today, we’ll recommend 2 products. Hope that you’ll be able to find one that suits your project!<\/p>\n\n\n\n
<\/div>\n\n\n\n8-Channel 12-Bit ADC for Raspberry Pi (STM32F030) ($9.90)<\/a><\/h3>\n\n\n\n
![\"\"](\"https:\/\/static-cdn.seeedstudio.com\/media\/catalog\/product\/cache\/9d0ce51a71ce6a79dfa2a98d65a0f0bd\/f\/r\/front_1_1.jpg\")
<\/figure><\/div>\n\n\n\nThis product is an 8-channel ADC based on STM32F030, this is perfect for consumer goods and temperature measurement. It is a cost-effective, low-power ARM Cortex M0 MCU as well!<\/p>\n\n\n\n
<\/div>\n\n\n\nFeatures:<\/p>\n\n\n\n
- Support Raspberry Pi 3B\/3B+\/4<\/li>
- CRC calculation unit<\/li>
- 5-channel direct memory access(DMA) controller<\/li>
- Serial wire debug (SWD)<\/li>
- Calendar RTC with alarm and periodic wakeup from Stop\/Standby<\/li>
- Real-time clock (RTC)<\/li>
- Timers:
- Advanced-control timer<\/li>
- General-purpose timers & Basic timers<\/li>
- Independent and system watchdog timers<\/li>
- SysTick timer <\/li><\/ul><\/li><\/ul>\n\n\n\n<\/div>\n\n\n\n
![\"\"](\"https:\/\/files.seeedstudio.com\/wiki\/8-Channel_12-Bit_ADC_for_Raspberry_Pi-STM32F030\/img\/280-pin.jpg\")
Overview<\/figcaption><\/figure><\/div>\n\n\n\n Later we will be using this ADC to demonstrate how to set up with Raspberry Pi as well!<\/p>\n\n\n\n
<\/div>\n\n\n\n4-Channel 16-Bit ADC for Raspberry Pi (ADS1115) ($10.95)<\/a><\/h3>\n\n\n\n
![\"\"](\"https:\/\/static-cdn.seeedstudio.com\/media\/catalog\/product\/cache\/9d0ce51a71ce6a79dfa2a98d65a0f0bd\/f\/r\/front_3.jpg\")
<\/figure><\/div>\n\n\n\nThis product is a 4-channel ADC based on Texas Instrument’s ADS1115, this is perfect for portable instrumentation and battery monitoring etc. It is a compact Raspberry Pi Zero form factor with integrated analog Grove connectors as well!<\/p>\n\n\n\n
<\/div>\n\n\n\nFeatures:<\/p>\n\n\n\n
- Support Raspberry Pi 3B\/3B+\/4<\/li>
- Wide supply voltage range<\/li>
- I2<\/sup>C-compatible serial interface<\/li>
- Input multiplexer (MUX) that provides two differential or four single-ended inputs.<\/li>
- Programmable data rate: 8SPS to 860SPS<\/li>
- Programmable comparator <\/li>
- Internal PGA<\/li>
- Internal low-drift voltage reference <\/li>
- Internal oscillator<\/li>
- LOW current consumption:
- Continuous Mode: Only 150\u03bcA<\/li>
- Single-Shot Mode: Auto Shut-Down <\/li><\/ul><\/li><\/ul>\n\n\n\n<\/div>\n\n\n\n
![\"\"](\"https:\/\/files.seeedstudio.com\/wiki\/4-Channel_16-Bit_ADC_for_Raspberry_Pi-ADS1115\/img\/pinout.png\")
Overview<\/figcaption><\/figure><\/div>\n\n\n\n
\n\n\n\nSetting up Raspberry Pi ADC<\/h2>\n\n\n\n
Bought a Raspberry Pi ADC but don’t know how to use it? Don’t fret! We will be showing you how to set up your Raspberry Pi ADC!<\/p>\n\n\n\n
What you’ll need:<\/p>\n\n\n\n
- Raspberry Pi<\/a> (3B\/3B+\/4)<\/li>
- Channel 12-Bit ADC for Raspberry Pi (STM32F030)<\/a><\/li>
- USB Cable<\/li><\/ul>\n\n\n\n
After you’ve gathered everything you need, you can follow the steps below:<\/p>\n\n\n\n
Hardware<\/h3>\n\n\n\n
Step 1: Insert the 8-Channel 12-Bit ADC for Raspberry Pi into Raspberry Pi<\/p>\n\n\n\n
Step 2: Connect the Raspberry Pi to PC through USB cable.<\/p>\n\n\n\n
<\/div>\n\n\n\nSoftware<\/h3>\n\n\n\n
Step 1: Download the source file by cloning the grove.py library.<\/p>\n\n\n\n
cd ~\ngit clone https:\/\/github.com\/Seeed-Studio\/grove.py<\/code><\/pre>\n\n\n\nStep 2: Install the grove.py library<\/p>\n\n\n\n
cd grove.py\n# Python2\nsudo pip install .\n# Python3\nsudo pip3 install .<\/code><\/pre>\n\n\n\nStep 3: Execute the below commands to run the code. <\/p>\n\n\n\n
cd grove.py\/grove\npython adc_8chan_12bit.py <\/code><\/pre>\n\n\n\nThe code below is the adc_8chan_12bit.py code.<\/p>\n\n\n\n
import time\nfrom grove.i2c import Bus\n \nADC_DEFAULT_IIC_ADDR = 0X04\n \nADC_CHAN_NUM = 8\n \nREG_RAW_DATA_START = 0X10\nREG_VOL_START = 0X20\nREG_RTO_START = 0X30\n \nREG_SET_ADDR = 0XC0\n \n \nclass Pi_hat_adc():\n def __init__(self,bus_num=1,addr=ADC_DEFAULT_IIC_ADDR):\n self.bus=Bus(bus_num)\n self.addr=addr\n \n \n #get all raw adc data,THe max value is 4095,cause it is 12 Bit ADC\n def get_all_adc_raw_data(self):\n array = []\n for i in range(ADC_CHAN_NUM): \n data=self.bus.read_i2c_block_data(self.addr,REG_RAW_DATA_START+i,2)\n val=data[1]<<8|data[0]\n array.append(val)\n return array\n \n def get_nchan_adc_raw_data(self,n):\n data=self.bus.read_i2c_block_data(self.addr,REG_RAW_DATA_START+n,2)\n val =data[1]<<8|data[0]\n return val\n #get all data with unit mv.\n def get_all_vol_milli_data(self):\n array = []\n for i in range(ADC_CHAN_NUM): \n data=self.bus.read_i2c_block_data(self.addr,REG_VOL_START+i,2)\n val=data[1]<<8|data[0]\n array.append(val)\n return array\n \n def get_nchan_vol_milli_data(self,n):\n data=self.bus.read_i2c_block_data(self.addr,REG_VOL_START+n,2)\n val =data[1]<<8|data[0]\n return val\n \n #get all data ratio,unit is 0.1%\n def get_all_ratio_0_1_data(self):\n array = []\n for i in range(ADC_CHAN_NUM): \n data=self.bus.read_i2c_block_data(self.addr,REG_RTO_START+i,2)\n val=data[1]<<8|data[0]\n array.append(val)\n return array\n \n def get_nchan_ratio_0_1_data(self,n):\n data=self.bus.read_i2c_block_data(self.addr,REG_RTO_START+n,2)\n val =data[1]<<8|data[0]\n return val\n \n \n \nADC = Pi_hat_adc()\ndef main():\n raw_data=ADC.get_all_adc_raw_data()\n vol_data=ADC.get_all_vol_milli_data()\n ratio_data=ADC.get_all_ratio_0_1_data()\n print(\"raw data for each channel:(1-8chan)(12 bit-max=4096):\")\n print(raw_data)\n print(\"voltage for each channel:(unit:mv,max=3300mv):\")\n print(vol_data)\n print (\"ratio for each channel(unit 0.1%,max=100.0%):\")\n print(ratio_data)\n \n print(\" \")\n print(\"NOTICE!!!:\")\n print(\"The default setting of ADC PIN is floating_input.\")\n print(\" \")\n \nif __name__ == '__main__':\n main()<\/code><\/pre>\n\n\n\nNow, if there’s no error, it should look like this!<\/p>\n\n\n\n
pi@raspberrypi:~\/grove.py\/grove $ python adc_8chan_12bit.py \nraw data for each channel:(1-8chan)(12 bit-max=4096):\n[2177, 2098, 2064, 2038, 2127, 2066, 2172, 2145]\nvoltage for each channel:(unit:mv,max=3300mv):\n[1599, 1741, 1668, 1658, 1644, 1787, 1694, 1677]\nratio for each channel(unit 0.1%,max=100.0%):\n[521, 544, 514, 504, 500, 559, 524, 505]\n \nNOTICE!!!:\nThe default setting of ADC PIN is floating_input.<\/code><\/pre>\n\n\n\n<\/div>\n\n\n\nStill uncertain about using a Raspberry Pi ADC? Here’s an example to help you:<\/p>\n\n\n\n
What you’ll need (including the items stated just now):<\/p>\n\n\n\n
- Grove – Sound Sensor<\/a> <\/li><\/ul>\n\n\n\n<\/div>\n\n\n\n
How to connect your hardware:<\/h3>\n\n\n\n
Step 1: Plug the 8-Channel 12-Bit ADC for Raspberry Pi into Raspberry Pi.<\/p>\n\n\n\n
Step 2: Connect the Grove – Sound Sensor to A0 port of the ADC module. <\/p>\n\n\n\n
Step 3: Connect the Raspberry Pi to PC through USB cable.<\/p>\n\n\n\n
It should look as such:<\/p>\n\n\n\n
![\"\"](\"https:\/\/files.seeedstudio.com\/wiki\/8-Channel_12-Bit_ADC_for_Raspberry_Pi-STM32F030\/img\/connection2.jpg\")
<\/figure><\/div>\n\n\n\n<\/div>\n\n\n\nSoftware<\/h3>\n\n\n\n
Tap the following command ++python grove_sound_sensor.py 0++ in the command line interface.<\/p>\n\n\n\n
pi@raspberrypi:~\/grove.py\/grove $ python grove_sound_sensor.py 0\nDetecting sound...\nSound value: 433\nSound value: 342\nSound value: 443\nSound value: 300\nSound value: 632\nSound value: 258\nSound value: 591\nSound value: 267\nSound value: 871\n^CTraceback (most recent call last):\n File \"grove_sound_sensor.py\", line 67, in <module>\n main()\n File \"grove_sound_sensor.py\", line 64, in main\n time.sleep(.3)\nKeyboardInterrupt<\/code><\/pre>\n\n\n\nYou can Ctrl + C whenever you wish to quit this program as well. And that is how you set up your Raspberry Pi ADC! <\/p>\n\n\n\n
Here are some useful links that would provide more details:<\/p>\n\n\n\n
- Datasheet STM32F030<\/a> <\/li>
- 8-Channel 12-Bit ADC for Raspberry Pi (STM32F030) Eagle Files<\/a> <\/li>
- 8-Channel 12-Bit ADC for Raspberry Pi (STM32F030) Software Library<\/a> <\/li><\/ul>\n\n\n\n
\n\n\n\nProjects with Raspberry Pi ADC<\/h2>\n\n\n\n
After learning how to set up your Raspberry Pi ADC, you’re now ready to explore the sea of projects out there! <\/p>\n\n\n\n
Raspberry Pi ADC Tutorial<\/a><\/h3>\n\n\n\n
- 8-Channel 12-Bit ADC for Raspberry Pi (STM32F030) Eagle Files<\/a> <\/li>
- Datasheet STM32F030<\/a> <\/li>
- Channel 12-Bit ADC for Raspberry Pi (STM32F030)<\/a><\/li>
- Raspberry Pi<\/a> (3B\/3B+\/4)<\/li>