The source code runs on STM32F4 Discovery board, and it was tested with actual real life measurements. Before I move into how the code is configured and how it works. I would like to start off by an brief explanation about how the SPI protocol works.
It is the master that controls the clock and initiates transactions by pulling the CS signal low. The master can address multiple slaves, but it can communicate only with one slave at a time. Besides setting up the clock frequency, the master also has to configure the clock polarity and phase with respect to the data. Mode 0 is the most common mode for SPI communication.
The MCU sends a request to read a certain ADC channel by sending a start bit, followed by a bit that defines if the ADC configuration is single ended or differential, followed by three bits for the channel address starting with the MSB bit: see table below as well for address configuration.
This time interval is generated with a timer interrupt. Notice in the interrupt service routine below that I just a flag to signal to the main loop that it is time to read an ADC channel.
It is very critical to make your service routine as short as possible. The ADC read function definition is defined below. Since the master sends 24 bits, it means twenty four clock cycles needs to be generated. The coursers show the time taken to send 24 bits. You are commenting using your WordPress. You are commenting using your Google account. You are commenting using your Twitter account. You are commenting using your Facebook account. Notify me of new comments via email.
Notify me of new posts via email. This site uses Akismet to reduce spam. Learn how your comment data is processed. Master configuration with three independent slaves Besides setting up the clock frequency, the master also has to configure the clock polarity and phase with respect to the data.But in all those articles, I used single channel of the ADC. The process remains same as using in single channel, with some addons though.
First we need to set up the channels, we want to read, under ADC. Here I will read Channels 0, 1 and internal temperature sensor The process is simple here. So here its goes. The value returned by channel 16 need to be converted inorder to get the temperature. The formula and the relative values are given in the datasheet.
Now we have to write a conversion complete function. It will be called whenever the conversion of the ADC values is completed. As to show that it works completely independent, I will blink a LED inside the while loop and the ADC values will be received separately from the while loop.
Hi, i have a problem with this code! In code 1, adc1 and adc2 are both scanned for hadc1, is this correct for multichannel? Do I need to create one more hadc2 if need to use keyline2? In code1, adc1 and adc2 both are scanned for hadc1, is it correct for multichannel reading? If keys are in different keyline then should it be scanned for hadc2?
Hello, I use a Stm32F and the first example dosent work for me. I have a problem with this code. The value of the first channel is right but the value of other channels is wrong.
Can you tell me the soloution for this problem? Thanks in advance for your answer. The second poll returns a timeout, and the values returned are clearly the same as the first. Is this mode really possible with the polling?I'm trying to get a simple ADC working on the stm32f4 discovery board. At the moment I simply want to obtain an input value ConvertedValue as a variable rather than saving to memory in DMA.
I'm struggling with the pins - some of them give me a little functionality and others none at all. I cant get any port to work properly. PIN0 will work to an extent - it will read a changing value, but it is also outputting a voltage of 2 volts which I've not told it to - and so any readings it gets are somewhat distorted.
I'd really appreciate anyone taking a look at the code im using its mostly taken from various sources around the web - not really my own. View all questions in Keil forum. Site Search User. Software Tools. Hi all, I'm trying to get a simple ADC working on the stm32f4 discovery board. Reply Cancel Cancel. More questions in this forum. All recent questions Unread questions Questions you've participated in Questions you've asked Unanswered questions Answered questions Questions with suggested answers Questions with no replies.
Not Answered. Started 18 hours ago by Saad Anees. Suggested Answer. Latest 1 day ago by adomanim. Number of clock cycles in the execution of "SysCtlDelay" in the simulator.
Keil Red Underline Problem 0. Started 1 day ago by ctarakci.Previously we have tried to do a single conversion of one ADC channel.
It is better to trigger conversion and wait for conversion complete interrupt. This way a processor can do other tasks rather than wait for ADC conversion complete.
This time we will go through another example where we will set up more than one channel and read ADC values using interrupt service routine. Bits  hold the number of ADC channel.
All 16 sequence channels can be set up same way through all SQR registers. Another thing we will have to take care of is to set up sample time for each channel. As we know each channel in sequence can be set for different conversion time. There are three bits for each channel in sequence.
Then we calculate an average value of each channel and later print results on terminal screen using UART. Once all data is stored in memory, a DMA transfer complete interrupt will be generated to trigger averaging and output. For the first eight channels, we will need to set up pins A0 to A7 as analog inputs.
How to read multichannel ADC in STM32
Then we can set up an ADC conversion mode. In peripheral library, this looks like:. Then we must enable to enable continuous conversion mode as we want to cycle through channel list several times:.
The next thing is to indicate which channels and what order we need to convert. For this, we set up each channel individually with commands:. But you can mess up the numbers as you like. After DMA copies predefined number of values, it generates an interrupt. Then we can manipulate data as we like. As in our example, we average multiple instances. Here is the complete main source code if you would like to analyze or use fragments for your purposes:.
Hi, could you check comments in your source code? It would be confusing sometimes. Fixed code. Please confirm if code works with this change. Thanks for a good site! But I take 4 readings for each channel and then average them to be printed. Of course you could go different way without storing all values then array of 4 would be enough. Hello, good tutorial.This means that it will map input voltages between 0 and 5 volts into integer values between 0 and It will map input voltages between 0 and 3.
The number of conversion steps is equal to the number of bits in the ADC converter. Each step is driven by the ADC clock. Each ADC clock produces one bit from result to output. The ADC internal design is based on the switched-capacitor technique.
Here the term 10 channel implies that there are 10 ADC pins using which we can measure analog voltage. The term bit implies the resolution of the ADC. The value will increase from 0 to based on the value of voltage per step, which can be calculated by formula.
When a input analog voltage is given to STM32 at its Analog inputs, the analog value is read and stored in a integer variable. That stored Analog value The connections are made according to the above given table. There are two Potentiometers present in the circuit, first one is used for voltage divider which can be used to vary voltage and provide analog input to STM Left pin of this potentiometer gets input positive voltage from STM32 3.
The other potentiometer is used to vary the contrast of the LCD display. It is same like arduino board. There is no need of changing the jumper pins of STM In this program will read the analog value and calculate the voltage with that value and then display both, analog and digital values, on the LCD screen. You can modify as per your requirements. Also make sure the function Liquid Crystal is called with the pin names that we just defined above.
As we discussed already, the microcontroller is a digital device and it cannot read voltages level directly. Using SAR technique the voltage level is mapped from 0 to The type of this variable is integer because we will only get values ranging from 0 to to be stored in this variable.
To do this we have the following formulae. In our case we already know that the ADC resolution of our microcontroller is The ADC value is also found in the previous line and stored the variable called val.
You can also measure the operating voltage by using a multimeter across the Vcc and ground pin on the board. So the above formula fits into our case as shown below.Cookie Notice.
A detailed tutorial on STM32 ADC
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There is a possibility to set the preemption priority for each interrupt in the NVIC so that the interrupt with higher priority can interrupt the lower priority one. There are a few interrupts generated by DMA controller - transfer complete, half-transfer complete and error. I would recommend you to go through it carefully to understand the principle.
What I would also recommend is to check return values of HAL functions. It will help you to reveal problems very fast in the future.STM32F4 Discovery board - Keil 5 IDE with CubeMX: Tutorial 11 LCD16x2 - Updated Dec 2017
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Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. I think your ADC interrupt handler is never called. Here is working code. I've already solved that problem. Invoking IRQ like I did in main is a bad idea.
STM32F4 SPI3 Interface with MCP3204T ADC
Asked 2 years, 4 months ago. Active 2 years, 4 months ago. Viewed 5k times. I would advice the bare register approach instead this bloatware. You have a very good polish tutorial here: elektroda. Active Oldest Votes. So your variable stays at 0. Guillaume Michel Guillaume Michel 1, 8 8 silver badges 12 12 bronze badges. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password.
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