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The scenario: I have a STM32 MCU, which uses an UART in DMA Mode with Idle Interrupt for RS485 data transfer. The baud rate of the UART is set in CubeMX, in this case to 115200. My Code works fine, when the Host uses the correct baud rate, it is also "long time" stable, no issues or worries.
BUT: when I set the wrong baud rate at the host, e.g. 56700 instead of 115200, the UART stops receiving data, even if I later set the baud rate at the host to the same baud rate the Microcontroller uses, it won't work. The only way to solve this issue so far is: reset the MCU and connect again with the correct baud rate.
To give you some (Pseudo-)Code:
uint8_t UART_Buf[128];
HAL_UART_Receive_DMA(&huart2, UART_Buf, 128);
__HAL_UART_ENABLE_IT(&huart2, UART_IT_IDLE);
Or in Plain Words: there is a UART Buffer for DMA (UART_Buf[128]) and the UART is started with HAL_UART_Receive_DMA(...), DMA Rx is set to circular mode in CubeMX, also the Idle-Interrupt is activated, using the HAL Macro: __HAL_UART_ENABLE_IT(...); This code works fine so far.
Works fine means:
when I transmit data from my PC to the Micro, the (one) Idle Interrupt is triggered (correctly) by the MCU. In the ISR I set a flag, to start the data parsing afterwards. I receive exactly the number of bytes I have sent, and all is fine.
BUT: when I make the wrong setting in my Terminal Program and instead of the (correct) baud rate of 115200, the baud rate select menu is set to e.g. 57600, the trouble begins:
The idle interrupt will still trigger after each transmission.
But it triggers 2-4 times in a quick "burst" (depending on the baud rate) and the number of bytes received is 0. I'd expect at least some bs data, but there is exactly 0 data in the buffer - which I can check with the debugger. There is obviously received nothing. When I change the baud rate in my terminal program and restart it, there is still nothing received on the MCU.
I could live with 0 received bytes, if the baud rate of the host is incorrect, but it's pretty uncool that one incoming transmission of a host with the wrong baud rate disables the UART until a hardware reset is done.
My attempts to resolve this were so far:
count the "Idle Interrupt Bursts" in combination with 0 received bytes to trigger a "self reset" routine, that stops the UART and restarts it, using the MX_USART2_UART_Init(); Routine. With zero effect. I can see the Idle Interrupt is still triggered correctly, but the buffer remains empty and no data is transferred into the buffer. The UART remains in a non-receiving state.
The Question
Has anyone out there experienced similar issues, and if yes: how did you solve that?
Additional Info: this happens on a STM32F030 as well as on a STM32G03x
When you send to the UART at the wrong baud rate it will appear to the receiver as framing errors and/or noise errors. It could also appear as random characters being received correctly, but this is less likely so don't be surprised to have nothing in your buffer.
When you are receiving with DMA, it is normal to turn the error interrupt on or else poll the error bits. When an error is detected you would then re-initialize everything and restart the DMA. This sounds like what you are trying to do by counting the idle interrupts, but you are just not checking the right bits.
If you don't want to do that, it is not impossible to imagine that you have nothing to do at the driver level and want to try to do the resynchronisation at a higher level (eg: start reading again and discard everything until a newline character) but you will have to bear in mind at least two things:
First, make sure you clear the DDRE bit in the USART_CR3 register. The name "DMA Disable on Reception Error" speaks for itself.
Second, the UART peripheral is able to self resynchronize, as long as you have an idle gap between bytes. If you switch the transmitter to the correct baud rate but keep blasting out data then the receiver may never correctly identify which bit is a start bit.
After investigating this issue a little bit further, i found a solution.
Abstract:
When a host connects to the MCU to an UART with an other baud rate than the UART is set to, it will go into an error state and stop DMA transmission to the RX Buffer. You can check if there is an error with the HAL_UART_GetError(...) function. If there is an error, stop the UART/DMA and restart it.
The Details:
First of all, it was not the DDRE bit in the USART_CR2 register. This was set to 0 by CubeMX. But the hint of Tom V led me into the right direction.
I tried to recover the UART by playing around with the register bits. I read through the UART section of the reference manual multiple times and tried to figure out, which bits to set in which order, to resolve the error condition manually.
What I found out:
When a transmission with the wrong baud rate is received by the UART the following changes in the UART Registers occur (on an STM32F030):
Control register 1 (USART_CR1) - Bit 8 (PEIE) goes from 1 to 0. PEIE is the Parity Interrupt Enable Bit.
Control register 2 (USART_CR2) - remains unchanged
Control register 3 (USART_CR3) - changes from 0d16449 to 0d16384, which means
Bit 0 (EIE - Error Interrupt enable) goes from 1 to 0
Bit 6 (DMAR - DMA enable receiver) goes from 1 to 0
Bit 14 (DEM - Driver enable mode) remains unchanged at 1
USART_CR3.DEM makes sense. I am using the RS485-Functionality of the F030, so the UART handles the Driver-Enable GPIO by itself.
the transition from 1 to 0 at USART_CR3.EIE and USART_CR3.DMAR are most probably the reason why no more data are transfered to the DMA buffer.
Besides that, the error Flags in the Interrupt and status register (USART_ISR) for ORE and FE are set. ORE stands for Overrun Error and FE for Frame Error. Although these bit can be cleared by writing a 1 to the corresponding bit of the Interrupt flag clear register (USART_ICR), the ErrorCode in the hUART Struct remains at the intial error value.
At the end of my try&error process, I managed to have all registers at the same values they had during valid transmissions, but there were still no bytes received. Whatever i tried, id had no effect. The UART remained in a non receiving state. So i decided to use the "brute force" approach and use the HAL functions, which I know they work.
Finally the solution is pretty simple:
if an Idle Interrupt is detected, but the number of received bytes is 0
=> check the Error-Status of the UART with HAL_UART_GetError(...)
If there is an error, stop the UART with HAL_UART_DMAStop(...) and restart it with HAL_UART_Receive_DMA(...)
The code:
if(RxLen) {
// normal execution, number of received bytes > 0
if(UA_RXCallback[i]) (*UA_RXCallback[i])(hUA); // exec RX callback function
} else {
if(HAL_UART_GetError(&huart2)) {
HAL_UART_DMAStop(&huart2); // STOP Uart
MX_USART2_UART_Init(); // INIT Uart
HAL_UART_Receive_DMA(&huart2, UA2_Buf, UA2_BufSz); // START Uart DMA
__HAL_UART_CLEAR_IDLEFLAG(&huart2); // Clear Idle IT-Flag
__HAL_UART_ENABLE_IT(&huart2, UART_IT_IDLE); // Enable Idle Interrupt
}
}
I had a similar issue. I'm using a DMA to receive data, and then periodically checking how many bytes were received. After a bit error, it would not recover. The solution for me was to first subscribe to ErrorCallback on the UART_HandleTypeDef.
In the error handler, I then call UART_Start_Receive_DMA(...) again. This seems to restart the UART and DMA without issue.
Hi I'm writing a kernel and plan to use MSI interrupt for PCI devices.
However, I'm also quite confused by the documentations.
My understanding about MSI are as follow:
From PCI device point of view:
Documentations indicate that I
need to find Capabillty ID = 0x05 to locate 3 registers: Message control (MCR), Message Address (MAR) and Message Data (MDR) registers
MCR provide control functionality for MSI interrupt,
MAR provide the physical address the PCI device
will write once interrupt occurs
MDR forms out the actual data it will write into the physical address
From CPU point of view:
Documentation shows that Message Address register contains fixed top of 0xFEE, and following by destination ID (LAPIC ID) and other controlling bits as follow:
The Message Data register will contain the following information, including the interrupt vector:
After reading all of these, I am thinking if the APIC_ID is 0x0h would the Message Address conflict with the Local APIC memory mapping? Although the address of FEE00000~FEE00010 are reserved.
In addition, is it true that the vector number in MDR is corresponding to the IDT vector number. In other words, if I put MAR = 0xFEE0000C (Destination ID = 0, Using logical APIC ID) and MDR = 0x0032 (edge trigger, Vector = 50) and enable the MSI interrupt, then once the device issues an interrupt CPU would correspondingly run the function pointed by IDT[50]? After that I write 0h to EOI register to end it?
Finally, according to the documentation, the upper 32 bit of MAR is not used? Can anyone help on this?
Thanks a lot!
Your understanding of how to detect and program MSI in a PCI (or PCIe) device is correct.*
The message address controls the destination (which CPU the interrupt is sent to), while the message data contains the vector number. For normal interrupts, all bits of the message data should be 0 except for the low 8 bits, which contain the vector.
The vector is an index into the IDT, so if the message data is 0x0032, the interrupt is delivered through entry 50 of the IDT.**
If the Destination ID in an interrupt message is 0, the Message Address of the MSI does match the default address of the local APIC, but they do not conflict, because the APIC can only be written by the CPU and MSIs can only be written by devices.
On x86 platforms, the upper 32 bits of the message address must be 0. This can be done by setting the upper part of the message address to 0 or by programming the device to use a 32-bit message address (in which case the upper message address register is not used). The PCI spec was designed to work with systems where 64-bit MSI addresses are used, but x86 systems never use the upper 32 bits of the message address.
Reprogramming the APIC base address by writing to the APIC_BASE MSR does not affect the address range used for MSI; it is always 0xFEExxxxx.
* You should also look at the MSI-X capability, because some devices support MSI-X but not MSI. MSI-X is a bit more flexible, which inevitably makes it a bit more complicated.
** When using the MSI capability, the message data isn't exactly the value in the Message Data Register (MDR). The MSI capability allows the device to use several contiguous vectors. When the device sends an interrupt message, it replaces the low bits of the MDR with a different value depending on the interrupt cause within the device.
I'm trying to get a code to work that triggers an interrupt for a variable data size coming to a RX input of a STM32 board (not discovery) in DMA Circular mode. ex.:CONNECTED\r\nDATAREQUEST\r\n
So far so good, I'm being able to receive data and all, while also triggering the DMA interrupt.
I will then create a sub RX message processing buffer breaking down each \r\n to a different char array pointer.
msgProcessingBuffer[0] = "COM_OK"
msgProcessingBuffer[1] = "DATAREQUEST"
msgProcessingBuffer[n] = "BlahBlahBlah"
My problem comes actually from the trigger of the interrupt. I would like to trigger the interrupt from any amount of data and processing any data received.
If I use the interrupt request bellow:
HAL_UART_Receive_DMA(&huart1,uart1RxMsgBuffer, 30);
The input buffer will take 30 bytes to trigger the interrupt, but that's too much time to wait because I would like to process the RX data as soon as a \r\n is found in the string. So I cannot wait for the full buffer to fill to begin processing it.
If I use the interrupt request bellow:
HAL_UART_Receive_DMA(&huart1,uart1RxMsgBuffer, 1;
It will trigger as I want, but there is no point on using DMA in this case because it will trigger the interrupt for every byte and will create a buffer of just 1 byte (duh) just like in "polling mode".
So my question is, how do I trigger the DMA for the first byte received but still receive/process all data that might come after it in a single interrupt? I believe I might be missing some basic concept here.
Best regards,
Blukrr
In short: HAL/SPL libraries don't provide such feachures.
Generally some MCUs, for example STM32F091VCT6 have hardware supporting of Modbus and byte flow analysis (interrupt by recieve some control byte) - so if you will use such MCU in you project, you can configure receive by circular DMA with interrupts by receive '\r' or '\n' byte.
And I repeat: HAL or SPL don't support this features, you can use it only throught work with registers (see reference manuals).
I was taking a look at some other forums and I've found there a work around for this problem.
I'm using a DMA in circular mode and then I monitor the NDTR which updates its value every time a byte is received through the UART interface. Then I cyclically call a function (in while 1 loop or in a cyclic interrupt handler) that break down each message part always looking for /n /r chars. This function also saves the current NDTR value for comparison if it has changed since the last "while 1" cycle. If the NDTR has changed since last cycle I wait a couple milliseconds to receive the remaining message (UART it's too slow to transmit) and then save those received messages in a char buffer array for post processing.
If you create a circular DMA buffer of about 50 bytes (HAL_UART_Receive_DMA(&huart1,uart1RxMsgBuffer, 50)) I think it's enough to compensate any fluctuations in the program cycle.
In the mean time I opened a ticket to ST and they confirmed what you just said they also added:
SOLUTION PROPOSED BY SUPPORTER - 14/4/2016 16:45:22 :
Hi Gilberto,
The DMA interrupt requests available are listed on Table 50 of the Reference Manual, RM0090, http://www.st.com/web/en/resource/technical/document/reference_manual/DM00031020.pdf. Therefore, basically, the DMA interrupt can only trigger at the end of one of these events.
• Half-transfer reached
• Transfer complete
• Transfer error
• Fifo error (overrun, underrun or FIFO level error)
• Direct mode error
Getting a DMA interrupt to trigger upon reception of a specific character in your receive data stream is not possible. You may want to trigger the interrupt when you receive packets of say 30 bytes each and then process the datastring to check if your \r\n chars have arrived so you can process the data block.
Regards,
MCU Tech Support
this will be my first time asking a question. First of all, I am just a programmer, I don't know much about electronics.
I am trying to communicate with a MCP9880 temeprature sensor through i2c, but I am getting weird readings in between 'real' ones, output looks like this (in decimal):
0 29
255 255
128 0
0 29
255 255
255 255
Here the 'real' lecture would be 128 0, but normally I get either 0xff or 0x1D as you can see. This happens reading any register. Also, other i2c devices are working as expected, but the many MCP9808 that we tried keep the same behaviour. Here's the code I use to read the temperature register (in bascom, I'm forced to use it :( )
I2cstart 'StartI2C.
I2cwbyte Wr_sensor1 'MCP9808 addr.
I2cwbyte &H05 'Temperature register
I2cstart 'StartsI2C.
I2cwbyte Rd_sensor1 'MCP9808 addr
I2crbyte Temp_1621 , Ack 'Read first byte
I2crbyte Temp_1621_dec , Nack 'Read second byte
I2cstop
The addresses are checked and correct, and I really think the code should be right. I keep saying this is an electronics issue, but keep saying they checked and everything is allright.
Thanks in advance.
PS: Here's a link to the datasheet http://ww1.microchip.com/downloads/en/DeviceDoc/25095A.pdf
Ok, I found the answer. Doing further tests, the device acted as if it resetted itself all the time. I suspected tiny voltage drops, so I researched the topic, plugged a capacitor, and that was it!
I hope this can help somebody :)
I'm trying to program an GPIO IRQ on AT91SAM9M10-EKES evaluation board.
I successfully registered the IRQ, and the IRQ is working.
However, some interrupts are missed. I'm sending 26, and I get only 22.
The code:
static irqreturn_t wiegand_interrupt(int irq, void *dev_id){
atomic_inc(&counter);
printk(KERN_WARNING "IRQ recieved, counting... %d\n",atomic_read(&counter));
return 0;
}
irq1 = gpio_to_irq(AT91_PIN_PA21);
if (irq1 < 0) {
err = irq1;
printk("Unable to get irq number for GPIO %d, error %d\n",AT91_PIN_PA21, err);
goto fail;
}
err = request_irq(irq1,wiegand_interrupt,0 ,"wiegand",NULL);
irq2 = gpio_to_irq(AT91_PIN_PA20);
if (irq2 < 0) {
err = irq2;
printk("Unable to get irq number for GPIO %d, error %d\n",AT91_PIN_PA21, err);
goto fail;
}
err = request_irq(irq2,wiegand_interrupt,0 ,"wiegand",NULL);
This is not the whole driver, but this is the actual part that deals with the IRQ.
If someone see a problem in the code, or can suggest a way to know why I lose 4 interrupts, please reply. I'm stuck on this for hours... :(
Thanks.
Ramon.
I assume you are triggering your interrupts with an external system (maybe a microcontroller or something that can toggle the GPIOS). Since I do not see a real ack of the interrupt, I assume the external system does not wait for the interrupt to be handled to maybe trigger a new one.
printk is a very slow function and that's why you can miss some interrupts: a new one can be triggered while you are still handling the previous one.
So I would advise not to use printk in the handler. If you want to achieve something like this, it would be better to use a tasklet or a workqueue as the bottom half of the interrupt handler.
I can only recommend the reading of the Chapter 10 of Linux Device Drivers.
Oh and by the way, your IRQ handler should not return 0 but IRQ_HANDLED.
Ok, actually, the problem is that I used the GPIO pins, while the GPIO pins don't support IRQF_TRIGGER_FALLING flag, which is exactly what I need. so probably, the interrupt handler doesn't recognize the signal correctly.
I found out that I need to use the external pins for IRQF_TRIGGER_FALLING enables IRQ's.