i wanted to use 4Mb baud rate of stm32f103 usart. how can i check that data received in PC are correct? I used hyper terminal but in its setting there is no 4Mb baud rate and when i run my code i receive wrong characters.but in low baud rates like 115200b data received correctly.
If the transmitter and receiver are not sending at the same speed, the receiver will erroneously read the data. Each byte has a start bit that synchronizes the receiver, and the remaining bits are determined by time.
Typical PC RS-232 serial ports only go up to 115200 bps. It is likely that your PC can't handle the 4 Mbps rate. I would recommend using 115200 or lower speed.
If you are communicating between devices and need higher speed, and just using the PC to debug, you could change the speed for debug purposes and set it faster once your comms are working. Alternatively, you could use a logic analyzer - This could be tedious to do manually, but some may have functions to read serial data.
If you have two of the stm32f19 modules, connect them using the USART at 4Mb, at then send a block of data with a checksum (or even a hardcoded block that you can compare). On the receiving unit, either confirm the checksum, or compare the data to see if the link works.
Related
I'm working on transceiving data on stm32F04xx. When I transmit data from the MCU at lower speed, it looks like if the baudrate was wrong and I get a bunch of question marks. When I increate transmission speed. I can read the data I'm sending. I've used to stm32cubeIDE to generate a simple UART code and only added
HAL_UART_Transmit(&huart2, "test\r\n", sizeof("test\r\n"), 1000);
HAL_Delay(500);
in the while loop.
On my NUCLEO-F042K6 evaluation board, I don't see any issues printing data on the tty port. But I have another device which uses the same stm32f042xx chip that only works when transmitting UART data at higher speed. so when i change my delay to something like 80 milliseconds, I can read the data flow.
I've attempted to flash the same binary that I flashed on my evaluation board on the other MCU I have but again the data only readable at higher transmission speed.
I'm flashing the MCU with stm32flash tool so I don't know if that can make a difference where on the eval board, I'm using the stm32cubeIDE to flash it.
I'm not sure what's going on here, I've tried different baudrates and different clock configurations and that doesn't seem to help too.
What could possibly cause the data to be unreadable like if the baudrate was wrong when transmitting at low speed?
I have a STM32F417IG microcontroller an external 16bit-DAC (TI DAC81404) that is supposed to generate a Signal with a sampling rate of 32kHz. The communication via SPI should not involve any CPU resources. That is why I want to use a timer triggered DMA to shift the data with a rate of 32kHz to the SPI data register in order to send the data to the DAC.
Information about the DAC
Whenever the DAC receives a channel address and the new corresponding 16bit value the DAC will renew its output voltage to the new received value. This is achieved by:
Pulling the CS/NSS/SYNC – pin to low
Sending the 24bit/3 byte long message and
Pulling the CS back to a high state
The first 8bit of the message are containing among other information the information where the output voltage should be applied. The next and concurrently the last 16bit are containing the new value.
Information about STM32
Unfortunately the microcontroller of ST are having a hardware problem with the NSS-pin. Starting the communication via SPI the NSS-pin is pulled low. Now the pin is low as long as SPI is enabled (. (reference manual page 877). That is sadly not the right way for communicate with device that are in need of a rise of the NSS after each message. A “solution” would be to toggle the NSS-pin manually as suggested in the manual (When a master is communicating with SPI slaves which need to be de-selected between transmissions, the NSS pin must be configured as GPIO or another GPIO must be used and toggled by software.)
Problem
If DMA is used the ordinary way the CPU is only used when starting the process. By toggling the NSS twice every 1/32000 s this leads to corresponding CPU interactions.
My question is whether I missed something in order to achieve a communication without CPU.
If not my goal is now to reduce the CPU processing time to a minimum. My pIan is to trigger DMA with a timer. So every 1/32k seconds the data register of SPI is filled with the 24bit data for the DAC.
The NSS could be toggled by a timer interrupt.
I have problems achieving it because I do not know how to link the timer with the DMA of the SPI using HAL-functions. Can anyone help me?
This is a tricky one. It might be difficult to avoid having one interrupt per sample with this combination of DAC and microcontroller.
However, one approach I would look at is to have the CS signal created as a timer output-compare (like PWM). You can use multiple channels of the same timer or link multiple timers to create a delay between the CS output and the DMA trigger. You should allow some room for jitter, because depending on what else is happening the DMA might not respond instantly. This won't hurt your DAC output signal though, because it only outputs the value on the rising edge of chip select (called SYNC in the DAC datasheet) which will still be from your first timer.
I'm testing the SPI capabilities of STM32H7. For this I'm using the SPI examples provided in STM32CubeH7 on 2 Nucleo-H743ZI boards. I will perhaps not keep this code in my own development, rigth now the goal is to understand how SPI is working and what bandwith I can get in the different modes (with DMA, with cache enabled or not, etc...).
I'd like to share the figures I've computed, as it doesn't seem very high. In the example, if I understood correctly, the CPU is # 400Mhz and the SPI bus frequency # 100MHz.
For polling mode I've measured the number of cycles of the call to function HAL_SPI_TransmitReceive.
For DMA I've measured between call to HAL_SPI_TransmitReceive_DMA and call to the transfer complete callback.
Measurements of cycles where made with SysTick clocked on internal clock. Since there is no low power usage, it should be accurate.
I've just modified ST's examples to send a buffer of 1KB.
I get around 200.000 CPU cycles in polling mode, which means around 2MB/s
And around 3MB/s in DMA mode.
Since the SPI clock runs at 100Mhz I would have expected much more, especially in DMA mode, what do you think ? Is there something wrong in my test procedure ?
I am looking to receive MIDI messages to control a microcontroller based synthesizer and I am working on understanding the MIDI protocol so I may implement a MIDI handler. I've read MIDI is transmitted at 31.25kHz without a dedicated clock line - must I sample the line at 31.25kHz with the microcontroller in order to receive MIDI bytes?
The MIDI specification says:
The hardware MIDI interface operates at 31.25 (+/- 1%) Kbaud, asynchronous, with a start bit, 8 data bits (D0 to D7), and a stop bit. […] Bytes are sent LSB first.
This describes a standard UART protocol; you can simply use the UART hardware that most microcontrollers have built in. (The baud rate of 31250 Hz was chosen because it can be easily derived from a 1 Mhz (or multiple) clock.)
If you really wanted to implement the receiver in software, you would sample the input signal at a higher rate to able to reliably detect the level in the middle of each bit; for details, see What exactly is the start bit error in UART? and How does UART know the difference between data bits and start/stop bits?
I'd like to send multiple signals (4 inputs and outputs and 7 outputs) from my Laptop to a microcontroller. I'm thinking of using a USB to serial converter and multiplexing the data through the port. I'll need to write codes both in the laptop end and in the microcontroller to multiplex the data.
Eg:
Tx of microcontroller:
1.Temperature sensor ADC output->Laptop
2.Voltage sensor to laptop
3.Current Sensor to Laptop
4.Photodiode current to Laptop
So I need to write a program in the microcontroller to send the data in this order. How can I accomplish this? I was thinking of an infinite loop which sends the data with time delays in between.
At the Rx pin of Microcontroller,
Seven bit sequences. Each bit sequence will be used to set the duty cycle of a PWM generated by the microcontroller.
I also need the same multiplexing or demultiplexing arrangement in the matlab end. Here too, I'm thinking of allotting some virtual 'channels' at different instants of time. What kind of algorithm would I need?
In case you always send all the inputs/outputs at the same rate, you could simply pack them into 'packets', which always start with one or more bytes with a fixed value that form a 'packet header'. The only risk is that one of the bytes of the sensor data might have the same value as the start-byte at the moment you try to start receiving bytes and you are not yet synchronized. You can reduce this risk by making the header longer, or by choosing a start-byte that is illegal output for the sensors (typically OxFF or so).
The sending loop on the microcontroller is really easy (pseudocode):
while True:
measure_sensors()
serial.send(START_BYTE)
serial.send(temperature)
serial.send(voltage)
serial.send(current)
serial.send(photodiode)
end while
The receiving loop is a bit more tricky, since it needs to synchronize first:
while True:
data = serial.receive()
if data != START_BYTE:
print 'not synced'
continue #restart at top of while
end if
temperature = serial.receive()
voltage = serial.receive()
current = serial.receive()
photodiode = serial.receive()
do_stuff_with_measurements()
end while
This same scheme can be used for communication in both directions.