Pages: .Программирование МК STM32. Урок 157. HAL. SPI. Interrupt
How to receive data via SPI. Sending is easy, but how do i receive? I will have other devices sharing the bus, so a dedicated line is needed.
Question is, what if I am in the middle of some other transmission? Re: How to receive data via SPI. You receive at the same time you send. Every time the clock pin goes active the Slave grabs the data on the MOSI line and shifts it into a shift register while the Master grabs the data from the MISO line and shifts it into a shift register. After 8 clocks the SPI. Typically the received data will lag behind the sent command by at least a byte since the Slave won't usually know what the Master wants until it has received an entire command.
The Master continues to send dummy data typically 0 to clock in the data from the Slave: Code: [Select]. Quote from: johnwasser on Aug 14,am. Quote from: casemod on Aug 14,pm. Now with Unlimited Eagle board sizes! Yes, you can have the slave send a signal to the master that indicates there is data to send. Once received, the master can then command a read sequence as John showed in his first reply.
Whether that signal is handled as an interrupt, or is a polled input by the master, the slave still cannot send until the master starts the transfer by taking the slaveSelectPin low and then doing the SPI.SD card reader, TFT display etc.
The names are as follows SPI is not very different from I2C. It just require more wires and the process of selecting the slave is a little different. This will disable the slave device. I have already wrote a tutorial about How to use this device with I2C.
Do check it out because I am not going to explain the register part but only focus on How to read and write data using SPI.
Below is the screenshot of the SPI setup window. This is for multibyte writing. It informs ADXL that we want to transfer more than one byte in a single transmission.
According to ADXL datasheet, this byte should be high if you want to do that. This is explained in my previous tutorial in detail. Anyway comments are self explanatory. This is it guys, You can download the code below. I have put the right values for the cpol and the cpha and my speed is less than 5MHz.
However, when i try getting the device ID i get rubbish the value changes each time i run the program and when i read the different axes I get really strange values especially for the z axis.
Basically, nothing is working.
The received data looks okay but there are 37 to 39 bytes in the buffer. Also with other byte numbers I receive 4 to 6 bytes more than expected.
After finishing the DMA the buffer content is processed in Sampling. The red part is excess data. The ADC delivers actual data here from its unused 12th channel. I bet as you do not protect the start transmition function call with any synchronisation mechanism flag, semaphore etc your interrupt is triggered before other transmit is done.
Also the mystery function sampling in the DMA handler may does something strange. Learn more. Asked 10 months ago. Active 10 months ago. Viewed times.
Does anyone have an idea why that happens? JanBurg JanBurg 21 2 2 bronze badges. How do you know that you have 5 bytes more?
Connecting 2 STM32 boards via SPI
What is your SplRxBuff size initialized? Active Oldest Votes. There is no other communication in between. The function Sampling is innocent.
Using the SPI interface on STM32 devices
There is no change when I comment it out. The additional bytes can be seen in the scope screenshot which I had attached to my post. SplRxBuff holds 40 bytes. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password.In this interface, in addition to transmit and receive lines, there is a third line that is used for clock line.
Each slave device also has a chip select enable pin, that is used for activating the device. SPI communication is different from other serial communication especially on data transfer. There is no concept like transmit and receive data, but there is a data trading concept. When data trading occurs, the data bits in master register is traded with the data bits in slave register on every clock from master one data bit per clock tick.
You can think SPI is like shift registers. There are 2 shift registers, one in master device and another in slave device.
The figure above illustrates the bit trading from master to slave. Master register contain data 0xFF and slave register contain data 0x After one clock tick, the master is left with seven of its original bits and the first one that is come in from the slave, and vice versa.
After a total of eight clock ticks, all eight bits of each byte have traded place. Sometimes not all data byte come from slave or sent to slave is meaningful. This happen because probably slave device has not received any command yet, so the data in slave register is not meaningful. The figure above is the timing diagram of SPI protocol.
We know that to communicate to the slave device, the slave select pin should be activated active low. The data is sampled every rising edge of clock. We can also sample data on falling edge of clock, this setting can be configured depending on the feature of the hardware SPI that you use.
In this example, master is send data byte 0x53 to slave and then slave send data byte 0x46 to master. This is the Arduino code for SPI slave device. You can get the project file from here. This is the result:. Go to the part 6 of the tutorial. Your email address will not be published. All source codes included. SPI slave Arduino. DelayInit. DelayUs 10. DelayMs. October 28, at PM. Leave a Reply Cancel reply Your email address will not be published. Do you want to deploy machine learning on microcontrollers?
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SnifMyBack Community Member asked a question. I normally don't need to ask question on forum because Google is a very good professor, but this time I'm not sure to have found enough informations.
It is done with the SPI 1 remapped. The thing is, the readed data make absolutely no sense. I know thought that the hardware and software work because on an other project based on stm32duino, the temperature reading is ok. So from what I can understand, it send one byte to receive one.
This is why I've change hspi1. Anyway sorry for the very long message and my not so good english, but if someone have an idea, I'll appreciate it. The Rx-only mode on SPI is tricky as it starts to clock immediately after you enable it and won't stop until you disable it; so it's relatively difficult to insert a chipselect GPIO manipulation into the stream of clocks.
On the other hand, in the "normal" bidirectional mode, clocks are output only when data written into the data register. The Tx bit does not need to be enabled i. This should cause no problem with Rx, so if the read data make no sense, you should investigate deeper. The best way is to connect a logic analyzer to the SPI lines and observe the data there. So after all I finally manage to get some time to work on the project. I've analyse the SPI signal. After coding my project differently, it still doesn't work.
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Let's do some math first. No idea about the data width, assuming 8 bit data it's 1. At MHz core speed it means that the interrupt handler has cycles to complete its task, or an overrun will occur. That's not a lot, but there are a few things that you can do about it.
Don't forget to declare as volatile everything that is used to communicate between the main program and the interrupt handler.
Ditching hal and writing your own isr can help as well. Keep in mind that an interrupt is processed by HAL after each byte received, even if the callback is called only once at the end of the buffer. I didn't realize HAL was processing so many interrupts, but taking a closer look at the code it now makes sense.Welcome, Guest.
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Could someone comment on the correctness of this code? Code: [Select]. Show us a bit more, don't be shy This code could be fine, or not, but it's not possible to comment unless at least the variable declarations and initial SPI setup are shown.
First shot in the dark: are Cmd and data correctly sized and typed? And what kind of "crash" is happening? Unhandled exception, infinite loop, or? Sure thing, here is an abridged version of the code. I've attached the full code below too if it helps. I am getting a hard fault on the uC. The weird thing is that it is almost always after the same amount of time about 8min 40s that it will crash. Try to trace back the code location of that exception. If your toolchain does not help you with it, you can look at the CPU regs and stacks.
No, not much to raise suspicion, at first look. I might go through the code more carefully later. I have some quick comments on the code, though: It seems to be affected by a bit of " cargo cult programming ", with repetitions and superfluous calls.