STM32 UART DMA and IDLE LINE || Receive unknown length DATA

[@ControllersTech]

TCM memories are not cacheable. So if your MCU have the DMA access to DTCMRAM, you can keep the buffer in the DTCM and you don't need the MPU setting. F7 Series MCUs are the examples of such kind. On the other hand some of the H7 series MCUs generate the code in DTCM RAM, but the DMA don't have access to it, so there you need to relocate the buffer to another SRAM, and configure the MPU. To sum it up, if the buffer is in the SRAM, no matter which one, you should configure the MPU.

[@Suresh_S_V]

Hi sir, I'm facing same issue which you shown in last part(rx buffer not storing). I'm using STM32H7A3ZI-Q Development board.can you share me the details, how to fix. Thanks for your video. .

[@ControllersTech]

Watch the cortex m7 playlist, the mpu configuration videos. This is not something which can be just fixed like that. You have to understand your mcu. Or start with the simpler controllers first.

[@Suresh_S_V]

@@ControllersTech Thanks for your quick response 👍 I will check it.

[@falling12]

Finally, something that isn't just a single send and receive! This video was super helpful. Thank you!

[@veisystems267]

At 8:25, line 114: It seems that the for-loop should go to "i

[@hiroshidenki4385]

You're a great engineer. Thank you very much for your work, you're amazing!

[@DerexArchives]

Thank you. These have been painful but enlightening learning sessions.

[@ahmetnsahi]

Türkiyeden selamlar eğer izleyip yapamıyorsanız main girmeden main üzerindeki init fonskiyonlarında, DMA init fonksiyonunu Usrat yada hangi periphal init ile kullanıyorsanız üstüne koymanız yeterli, iyi çalışmlar...Aksi takdirde son biti okuyor gerisini okumuyor. Sorun priority elle yapılması gergtigini söylüyor.

[@pinglag8546]

@ahmetsahin4901 Denedim ve çalıştı. Bilgi paylaşımı için teşekkürler. Gömülü sistem programları yazmaya yeni başladım sayılır cubemx sorunları yüzünden saatler harcıyorum ya hep böyle mi devam edecek bilmiyorum.

[@ahmetnsahi]

@@pinglag8546 sana tavsiyem algoritma ögrendiyesen low level standart libary tarzı kodlamaya bak sadece stm ile artık piyasa yürümüyor nuvoton vb firma işlmecilerini de yazıyor olmak lazım malüm fiyatları uctu piyasanın

[@pinglag8546]

@@ahmetnsahi haklısın fakat biraz daha donanımları tanımak kabiliyetlerini hızlı keşfetmek için stm tercih ediyorum yoksa denetleyiciler farklı komutlarla (bazı küçük farklılıkları saymazsak) aynı işleri yapıyorlar.

[@KervanASLAN]

Selamlar, Main fonksiyonunun üstü böyle, void SystemClock_Config(void); static void MX_GPIO_Init(void); static void MX_DMA_Init(void); static void MX_TIM2_Init(void); static void MX_USART1_UART_Init(void); static void MX_USART2_UART_Init(void); static void MX_TIM3_Init(void); Fakat yine de çalışmıyor, başka sorun olabilir mi?

[@pinglag8546]

@@KervanASLAN bu kısım init fonksiyonlarının tanımlandığı kısım. Senin bu fonksiyonların çağrıldığı kısmı kontrol etmen gerekiyor.

[@minayakarimova]

I was waiting too, great thanks for your all support

[@bobby9568]

was waiting for this one, thanks!

[@dnyaneshvarsalve2984]

This time implemented UART DMA, Thank you Controllers Tech

[@co0lxer]

Hello. My IDLE interrupt not working properly. My Buffer size is up to 255, but IDLE is calling after 16 characters. If i place transmit feedback here i receiving it few times. It looks like idle time is too short?

[@co0lxer]

Ok When I decreased the UART Baudrate it almost working fine. On the new baudrate i can achive up to 512 characters at a time, but sometimes is 256, even if configured twice more. Why is it?

[@egar1956]

Thank for this video, I found very useful for L86 modules

[@samsman007]

@12:10 So how to tell when the reception is complete to start processing the data?

[@ControllersTech]

We don't. Basically if you are using a computer to send the data, it will show the progress. You can implement some character sequence at the end of the file and then check it in the STM32. You can also check the final buffer size to match with the filesize. Anway you can start processing the data as soon as the first chunk arrives. By the time you finish processing the first chunk, the second one will arrive. And whe. You reach the null character, that means the reception is finshed.

[@1over137]

I have been trying to make a USB serial tap for debugging (tap both Rx and Tx and send them out the USB VCOM port). The issue I had and I've only now figure it out... and as a warning to yourself and your code.. I was testing with an ESP 12F AT command channel. When I ran my STM32 app the module was usually sitting idle doing nothing. So I would pull it's RESET pin low and wait for my app to fire the interrupt for the boot output and eventually "ready". Nothing happened. No data. No call backs, nothing. Hmmm. It was only when I put a logic analyser on the serial line that the "penny dropped". By pulling the reset line low to reset the ESP it generates "break condition" in the UART signal until it comes back up again. That break condition aborts the DMA transfer. The abort does not call the RxEventCall back as no data is received. If you don't take care to resume your DMA Rx on such a fault condition, your code will most likely dead lock.

[@Theo005-k5e]

Unlike you did in the video if I enable the UART interrupt I receive only the last character of the string.I disabled it and it works perfectly fine(I suppose it has something to do with the RXNE bit).Could you tell me why is works only with the global interrupt disabled?

[@behnammadadnia3410]

Thank you for the nice video, would you please let me know what is the value of SIZE in the code?

[@usmanhaider4653]

Great work. Your videos made my life easy.

[@baldebaldemord9588]

Very nice! I'm a bit of a beginner when it comes to dma. For some reason I only recive the last character I send with this method. I use an STMF373VB. The HAL_UARTEx_ReceiveToIdle_DMA Interrupt gets triggerd correctly but in my RX-Buffer only the last character is present. The strange thing is, that the Size transfered to the Interrupt is correct.

[@ControllersTech]

Rx buffer is supposed to have the recent characters. That's why we have another buffer, main buffer, where we save the previous data as well as the new one

[@baldebaldemord9588]

@@ControllersTech The problem was the Baude-Rate actually. I set it to 115200 but the max for my chip is 38400.

[@leonelcra]

Be sure the DMA is initialized before the UART

[@facundoquiroga2276]

​@@leonelcra Great! It worked for me. I had the same problem as Balde. Thanks to both of you.

[@indyzd]

@@leonelcra Awesome advice! Would you mind letting me know why initializing the DMA before UART solves that problem?

[@JesusChrist-sx1lf]

Why isn't circular mode working? Any particular reason? Isn't the callback function called just as before with normal mode?

[@ControllersTech]

Ofcourse it can work, but then you write your own code to handle the data in the buffers..

[@eliasdrotleff5987]

By doing that, you save the second buffer.

[@rajabmur4311]

thank you sir , that was helpful. but I don't understand why the data didn't overlap when you sent the large file? you said it was sent by chunks but how did that happen, is it a feature in UART? that data was sent at once so how the IDLE state took place? and I am confused about the copying process, it takes sometime and we might miss some data meanwhile right? but that didn't happen

[@MrHause13]

Thank you fot another important video. Looking forward for the explanation of this cacheable memory and why we need to configure MPU. You set the address of the MPU to the read address where RxBuffer is placed. But when you then declare some other buffer before RxBuffer the address of the RxBuffer will move and will not be correct for this defined in MPU. In small project it is under controll but in bigger project it seems to be hard to keep it under control. Maybe I don't understand something properly so I wait nervous for next videos. Good job! PS. When I move the RxBuffer to the other SRAM, do I still have to configure MPU?

[@ControllersTech]

Yes the rxbuffer will move and that's why in big projects, we have to be really careful about this. I have explained in the previous video about fixing the location of rxbuffer. Regarding the movement of the rxbuffer, check the pinned comment.

[@adamli9718]

Thanks for sharing!!!It's very clear and comprehensive!!! And I got some question about using API function about uart and dma. I've have used some other api like `HAL_UART_Receive_DMA` and write the Interrupt Service function in `UARTx_IRQHandler` in `stm32h7xx_it.c`. But in vedio you just use another API seems in more low level driver like `HAL_UARTEx_RxEventCallback` and `HAL_UARTEx_ReceiveToIdle_DMA`. Is there some knowledge about how to choose thoes APi , if there I would appreciate to hear from you thanks!!!

[@ControllersTech]

APIs changes based on what you want to do. The video title says IDLE line so I have used the IDLE Line related API. How to choose ? Well read reference manual, understand the functions of the peripheral, then look for relatable APIs in the peripheral's header and source files.

[@vinhphamquang8209]

Hi, thanks for this video. I'm new and not familiar so much with stm32, so can you make a guide how to use this with the ring buffer, and can you modified the code like you said at 10:18 :v I want to get a buffer receiving from uart (large data, json format) and store it in a "string", like arudino. Can I use malloc, realloc for MainBuffer and then free it? Because in the video I saw that the main buffer is overlapsed when receiving huge data and I have to get the string out of that buffer, but you said dont do a lot of works there ( it can disturb the receiving progress).

[@ControllersTech]

Yeah i will write that code soon. I am not getting enough time for it. I'll try Probably this weekend. You can use malloc, but the point is when exactly are u going to free the memory ? You can't do the entire processing in the callback, or else you won't get the new data. If the data is huge, and you don't want to overlap, then create a big main buffer. Do the processing in the while loop, or create another function for it.

[@esserfranz-juergen5886]

Many thanks for Your great explanation, which helped we very well !

[@shettymalnad1978]

Am facing issue receive unknown length from USART_Receive_IT but i dont want to use DMA how can i achive ?

[@bingo3463]

07:31 what happen if we get more 10 bytes (> RxBuf_SIZE)?

[@ControllersTech]

Then the interrupt is triggered for 10 bytes. The remaining could remain intact or could get lost... It's uncertain.

[@utkudenizaltiok860]

Hi I had a weird problem would be happy if you can help I am trying to commiuncate 2 stm32 (one transmits in DMA a text in every second and the other recevies in DMA). Transmitting one has no problem works well But When I type this code in the "int main(void) USER CODE BEGIN 2" of Receiver (as you did in ur video) " HAL_UARTEx_ReceiveToIdle_DMA(&huart2, received, received_size); __HAL_DMA_DISABLE_IT(&hdma_usart2_rx, DMA_IT_HT); " if I don't put anything in "while (1") part it doesn't receive and read it just stays idle but when I put the upper code in "while(1)" it starts to read But in your video you didn't use while part at all and it still works why ? Can you explain ? Thanks

[@KervanASLAN]

Üstadım, çözüm buldunuz mu? Bende de aynı sorun var. Video video geziyorum :) Bu arada STM32F1xx'ler STM32F4'lerden farklı davranıyor sanıyorum, bu videolarda olan şeyler STM32f1xx'de olmuyor.

[@alejandrovargas079]

Hi, may you help me, please, when I put parity only received a byte, or when I Changed the bauds as well, do you Know what its the problem???

Thank you so much. I worked this tutorial on F0 series. But it doesn't work on L0. I am sending and receiving irrelevant data. RxEventCallback function never called.

[@enginkamanl3574]

I am using the L4 series.When break point is put,function called but.When break point is not put,function no called.I not understand.Can you give me help

[@markoa1310]

I cant use HAL_UARTEx_ReceiveToIdle_DAM callback on STM32F417, because extended library is not included? Is IDLE line detection possible only on F7 family?

[@ControllersTech]

That tutorial was made on f446. Also i have tested on f103, f407,f411 too.

[@klaus9503]

Not working for me... no interrupt gets called.

[@ControllersTech]

What MCU ? Also check with the simple uart receive if that's working or not.

[@klaus9503]

​@@ControllersTech I finally found the problem. The problem was that the DMA only works in the D2 RAM. From the datasheet: "Two dual-port DMAs (DMA1, DMA2) located in D2 domain, ...". I use the STM32H743VI MCU. Now I just created a pointer to that region instead of a array buffer.

[@dailyboost06]

I have a similar problem, STM32L496RE. couldnot enter the interrupt.How did you solve it?

[@XxDaafgXx]

Do you have anything in regards to the data communication between a Raspberry pi 4 and Stm32? Would this video take me in the right direction?

[@ControllersTech]

Uart is the easiest way to communicate. If the data length is known, you can simply use hal uart receive function. This is typically used for unknown data length.

[@XxDaafgXx]

@@ControllersTech Do you have a video for that code's set up anywhere between a Raspberry Pi 4 and Stm32? I am a tad inexperienced with the STM32IDE set up -> and communication between the two devices through UART, Just wondering is all, it's okay if you don't, I should be able to figure it out eventually, thanks for replying

[@ControllersTech]

Check out the playlist STM32 UART: kzbin.info/aero/PLfIJKC1ud8gjhc4HiqVXUzcVq4iL5MqTz Video no. 6 and 7 are the easiest way to communicate using UART.

[@XxDaafgXx]

@@ControllersTech Okay cool, I understand the set up for the STM32 for TX and RX (Transmitting and Receiving), now what would I have to do with the Raspberry Pi in order for it to do the same thing and essentially communicate with the STM32 in the same manner via POLLING through Usart, Any Advice? Thanks for your help so far

[@KSITREVS]

Thank you for another video, when will you be exploring USB? Im interested in making a custom USB device which i can pass data too. USART is cool, but a custom USB name and driver would be a good project which not many youtubers are capable of doing! A good starting point would be the Open Source Helios Laser controller which uses a SAM4 STM chips

[@exaltedcodiing6655]

Can we increase the idle event time? so that complete unknown data can be achieved and after that event interrupt occurs. in my case first, 5 bytes transfer abruptly and the remaining bytes transfer after a little conversion. but I need all the bytes at the same event occur.

[@ControllersTech]

you can use simple uart receive function. It have the timeout feature, so even if the buffer is not filled, the timeout can occur and you can process the received data

[@migmelccs]

Why idle interrupt is always combined with DMA? Is it possible to receive data using idle interrupt without DMA?

[@ControllersTech]

"always" ? Of course you can make it work using idle line interrupt without dma

[@migmelccs]

@@ControllersTech How would you do it? Combined with RXNE interrupt?

[@ShivaKumar-or4qs]

thank you for your valuable videos. it is very helpful

[@sakugava]

Very useful post. I´ll test soon.

[@ControllersTech]

Please do. I need feedback to improve it 😸

[@lukaspetrikas6320]

Great tutorial. at 7:50 you explain how to fix the issues with the mainbuffer not appending the data correctly. Just a quick question though: void HAL_UARTEx_RxEventCallback(UART_HandleTypeDef *huart, uint16_t Size) { if(huart->Instance == USART3) { memset(aMainBuffer, 0, sizeof(aMainBuffer)); memcpy(aMainBuffer,aRxBuffer,Size); HAL_UARTEx_ReceiveToIdle_DMA(&huart3, aRxBuffer, RXBUFFERSIZE); __HAL_DMA_DISABLE_IT(&hdma_usart3_rx,DMA_IT_HT); } } Your solution seems quite complex. Why dont you just reset the main buffer everytime the eventcallback is triggered, that way, everytime you copy rxbuffer to mainbuffer mainbuffer is emtpy.

[@ControllersTech]

Because main buffer is suppose to store data which can be processed later. If we reset it everytime the event is triggered, then there is no difference between rx buffer and main buffer

[@lukaspetrikas6320]

@@ControllersTech ahh i see. The data will remain there but only till you receive a new command .

[@1over137]

@@ControllersTech When I did this (double buffering) for DMA transfers (readying bursty high rate MQTT messages), I instead created an array of buffers. uint8_t buffers[COUNT][SIZE]; Then circularly loop the buffers with a head (processing reading) and tail (DMA call back writing). I was however matching on protocol headers with a start byte and a message length, so I could get each message in a buffer on it's own. I ended up needing this because to two things conspiring. On start up I had to render the display background etc. At the same time the messages would start flowing on the UART and because the system had just connected it was going to possibly receive a large burst of queued messages. Combined this caused buffer overruns which I didn't like. So I increased the buffer count from 2 to 8 and didn't drop a single message on start up :)

[@naasikhendricks1501]

&hdma_usart2_rx the typedef was not initialization was not happening. It was declared. So I had to static as way to force the typedef to take hold.

[@markoa1310]

If I disconect UART wires from and reconnect again the UART doesnt work any more? Do you have any suggestion regarding that?

[@ControllersTech]

Don't disconnect wires 👍

[@ShashikantMourya-o7l]

Can you tell me how to receive data from TFmini Plus LiDAR Module , This is distance sensor, it is send data very frequently So tell me how can I manage.

[@basmaal-ghali9174]

Thanks. Could you, please make a video about: adc, dual mode , dma

[@pdeepakjayan1993]

Sir Can I use the same code to receive gps data(135bytes) each second. What is the value I must provide for Rxbuf size and Mainbuf size??

[@ControllersTech]

Depnds on how the data is sent by the gps device. I tried using it with the neo6m, but it was not working for some reason. You can try it.. for 135 bytes, you can just set the Rx buf of similar size lile 140 bytes.. and set the main buf of twice it.. If it doesn't work, check out the gps video on this channel. I covered another way of receiving unknown length data (using head and tail method) and it worked for the gps..

[@jnchacon]

I have try it but it does not work. I copy it to the letter.

[@vantoanmai5670]

Hello, does it work on the MCU F103 line?

[@dholakiyaparth]

This was very helpful. Thank you

[@dnyaneshvarsalve2984]

hello Controllers Tech, I have use this function HAL_UARTEx_ReceiveToIdle_IT(&huart4, rx_buf, rx_buf_size); and successfully able to get rx data. Please tell me how to adjust timeout for this function, since i want increase idle timeout my my application

[@ControllersTech]

Idle line doesn't work like that. You can't adjust the timeout for IDLE line. Basically it depends on baud rate. Say if the baud rate is 1000bps means 1000 bits per second. The time between each bit is 1ms. Then if no bit is received for 1ms, the idle line interrupt gets triggered.

[@dnyaneshvarsalve2984]

@@ControllersTech thanks for the info

[@zaferaltun]

Thank you very much, keep going!

[@dymastro788]

Perfect, nice video again

[@AhmadAsmndr]

thank you very much very helpful!

[@mithileshgaikwad7180]

At line no 114 , how you get the data length

[@ControllersTech]

Line 114 is to check for the OK string.

[@shahafyehuda472]

Very helpful thanks

[@StudentoftheUniverse-f7z]

Almost impossible to see your screen with the dark black background and tiny font.

[@jacewalton6677]

why not just use the DMA in circular mode?

[@ControllersTech]

Because it was getting harder to code with circular buffer.

[@naimmasri9495]

Not working on stm32h743VI help please

[@ControllersTech]

Watch the cortex m7 playlist, the STM32 MPU Config series videos. Literally mentioned at 12:50

[@naimmasri9495]

@@ControllersTech ok thank you.

[@Suresh_S_V]

​@Naim Masri did you solved this issue?

[@tonyguo3619]

That is very helpful, thanks.

[@ssarpakai]

Why are we using usart2 always.

[@mohamedraqi1291]

GREAT BRO !

[@edouardmalot51]

VERY INTERESTING, THANKS

[@bingo3463]

Please make new video. Send file .txt over UART and save it in SD card...

[@ControllersTech]

Soon

[@vigneshwaransaminathan6418]

Super 👍

[@georgestoikos1034]

you get a hardfault in stm32h7a3 with mpu

[@ControllersTech]

What's the address of rx buffer ?

[@georgestoikos1034]

@@ControllersTech I added them to a section and modified linker script to place them on ram. 0x24000000

[@ControllersTech]

I have tested it for h7a3, and it works well for the same memory address like your. You must be doing something wrong. Check in the memory details if the rx buffer is showing up at the new location. Try simple memset operation on rx buffer to check if it causes hardfault

[@georgestoikos1034]

@@ControllersTech should we use mpu ONLY if the buffer sits on DTCMRAM (0x20000000)? Does mpu and buffer relocation cause the hardfault? I have relocated the buffer to RAM. Everything seems to be working with just the relocation. I believe I followed your tutorials precisely . its a brand new nucleo stm32h7a3 board. I got the memory address from the memory explorer. I will try once again leaving the buffer at DTCMRAM (0x20000000). I am 99% sure I didn't miss any step

[@ControllersTech]

Like i said i tested with the same address and it worked perfectly. Send me your main file @telegram or discord or mail

[@dineshganesh6723]

Very helpful tq