I want to use a sensor with one-wire protocol, the matter is which way of using this protocol is optimized and more rational? over usart or using bit banging?
if it is important I'm using am2305 and stm32fxx microcontrollers.
I'm prefer to use USART+DMA with one buffer for transmit and receive. And I think this choice depends on your skill and requierements of your project.
There many ways to implement one-wire protocol.
exti interrupts + timer base mode
timer input capture + dma
usart interrupts
usart (err interrupts only) + dma
All of them have thier advantages and disadvantages:
busy or free pins
busy or free periferals (tim, usart)
busy or free dma channels
lower or higher frequency of interrupts in programm
easy or hard for implement it
I have different projects where work first and last methods listed above.
You must know which method is preferred for you and your project.
Related
I am wondering if there is a user-definable, built-in ISR function in the HAL library that triggers as soon as a byte is received in the SPIx Rx buffer on STM32L4xx MCU? For instance, as a startup test, I would like to send one byte (0xBC) from a Master STM32L452 nucleo board via SPI2 to a Slave STM32L452 nucleo board. Once the Slave board receives the byte, it flashes LED2, and transmits a different byte (0xCD) back to the Master. Once the Master receives the byte, it flashes LED2 as confirmation. I have initialized both boards as Master/Slave, enabled DMA and global interrupts, 8 bits per transfer using MXcube. I can achieve what I want using the HAL_SPI_Transmit_DMA() and HAL_SPI_Receive_DMA() functions and delays written into the while(1) portion of my main routine (as below). However, I would like to achieve the same using an ISR function that automatically executes once a byte is received into the SPI Rx Buffer.
Master Code:
uint8_t spiDataReceive = 0;
uint8_t spiDataTransmit = 0xBC;
while(1) {
if(!HAL_GPIO_ReadPin(GPIOC, GPIO_PIN_13)) {
//Transmit byte 0xBC to Slave and Receive Response
HAL_SPI_Transmit_DMA(&hspi2, &spiDataTransmit, 1);
HAL_Delay(20);
HAL_SPI_Receive_DMA(&hspi2, &spiDataReceive, 1);
if(spiDataReceive == 0xCD) {
flashLED2();
spiDataReceive = 0x00;
}
}
}
Slave Code:
uint8_t spiDataReceive = 0;
uint8_t spiDataTransmit = 0xCD;
while(1) {
HAL_SPI_Receive_DMA(&hspi2, &spiDataReceive, 1);
HAL_Delay(10);
if(spiDataReceive == 0xBC) {
HAL_SPI_Transmit_DMA(&hspi2, &spiDataTransmit, 1);
flashLED2();
spiDataReceive = 0x00;
}
}
No library is needed. You need to set RNEIE bit in the SPI CR register and enable in the NVIC the interrupt. 2 lines of code. No libraries needed.
The only needed resource is the Reference Manual from the STM website.
Yes, the HAL provides user callbacks. In order to use those, you have to activate the corresponding interrupt in NVIC and have the HAL handler called by the interrupt vector table (please have a look at stm32l4xx_it.c, too).
But before you do so, you should consider the following questions:
If you feel confused or frustrated by the complexity of ST HAL libraries, read the Reference Manual and follow the advice of P__J__ (see other answer).
If you feel confused or frustrated by the complexity of the hardware interface, follow the present answer.
Both HAL_SPI_Transmit_DMA() and HAL_SPI_Transmit_IT() support a variable number of transfer bytes.
If all you are going to need is that one-byte transfer, HAL functions may be an overkill.
Their advantage is that you can run some C library functions without dealing with HW register access in C (if that is quite new to you, coming from the arduino ecosystem). And of course, to transfer more than a single byte through the same interface when you extend your application.
You should decide whether you want to get an interrupt from the DMA you have tied to the UART, or if you want to avoid the DMA and get the interrupt from the UART itself. From my point of view, you should really not trigger an ISR by the same interrupt event which is used to start a DMA transfer to fetch the data!
In the same way as you find a description of the HW registers in the
Reference Manual and
Data Sheet of the controller, you find documentation on the HAL (layering concept, usage requirements etc.) in the
User manual of STM32L4/L4+ HAL and low-layer drivers
(see sections 70 and 102, resp., and chapter 3).
Of course, this interface aims mostly for abstraction and portability whereas directly addressing the HW interface usually allows much better efficiency in terms of latency/CPU load, and ROM/RAM usage. The "Low-Level" library drivers aim for a certain compromise, but if you are new to this whole topic and unsure what to start with, you should either start from the HW register interface, or from the portable HAL library API.
If the specification documents (HW or Lib description) are too abstract for you and you prefer some hands-on information source, you may want to first have a look at STM32Cube firmware examples for STM32CubeL4.
These also include SPI data exchange use cases (SPI_FullDuplex_ComIT for example) that are available for NUCLEO-L4532RE (and others) and described in application note AN4726 (page 16).
In addition to the interrupt selection/handling, you should check two more aspects of your program:
If you get an interrupt from the hardware, there is no reason for the HAL_Delay() calls.
Keep in mind that on SPI, you can only "return" data from slave to master while the master is transferring data (which may be zero data).
Otherwise, the "transmit" call on the slave side will only put data into the TX register, and the SPI peripheral will wait infinitely for the SCK trigger from the master...
describe how a JTAG connection is used to test the circuitry in a chip using just 5 pins
JTAG is used as a synonyme for the boundary scan protocol, see
- https://en.wikipedia.org/wiki/JTAG#Boundary_scan_testing
- https://en.wikipedia.org/wiki/Boundary_scan
It was the Joint Test Action Group (JTAG) who originally devised this protocol for testing circuitry around chips.
Besides this original purpose, the same protocol is used to program and debug CPUs, FPGAs etc.
In order to use JTAG, you need an adapter device that supports the circuitry you would like to test/debug.
[...] using just 5 pins
You are wondering how to test the entire chip through "just" 5 pins? To get a rough idea, think of a shift register similar to UART and SPI (but keep in mind that JTAG is notably more sophisticated).
I am using a STM32L476RG board and HAL SPI functions:
HAL_SPI_Transmit(&hspi2, &ReadAddr, 1, HAL_MAX_DELAY);
HAL_SPI_Receive(&hspi2, pBuffer, 4, HAL_MAX_DELAY);
I need to receive data from accelerometer's buffer with maximum speed and I have a problem with delay in these functions. As you can see on the oscilloscope screenshots, there are several microseconds during which nothing happens. I have no idea how to minimize the transmission gap.
I tried using HAL_SPI_Receive_DMA function and this delay was even bigger. Do you have any idea how to solve this problem using HAL functions or any pointers on how I could write my SPI function without these delays?
TL;DR Don't use HAL, write your transfer functions using the Reference Manual.
HAL is hopelessly overcomplicated for time-critical tasks (among others). Just look at the HAL_SPI_Transmit() function, it's over 60 lines of code till it gets to actually touching the Data Register. HAL will first mark the port access structure as busy even when there is no multitasking OS in sight, validates the function parameters, stores them in the hspi structure for no apparent reason, then goes on figuring out what mode SPI is in, etc. It's not necessary to check timeouts in SPI master mode either, because master controls all bus timings, if it can't get out a byte in a finite amount of time, then the port initialization is wrong, period.
Without HAL, it's a lot simpler. First, figure out what should go into the control registers, set CR1 and CR2 accordingly.
void SPIx_Init() {
/* full duplex master, 8 bit transfer, default phase and polarity */
SPIx->CR1 = SPI_CR1_MSTR | SPI_CR1_SPE | SPI_CR1_SSM | SPI_CR1_SSI;
/* Disable receive FIFO, it'd complicate things when there is an odd number of bytes to transfer */
SPIx->CR2 = SPI_CR2_FRXTH;
}
This initialization assumes that Slave Select (NSS or CS#) is handled by separate GPIO pins. If you want CS# managed by the SPI peripheral, then look up Slave select (NSS) pin management in the Reference Manual.
Note that a full duplex SPI connection can not just transmit or receive, it always does both simultaneously. If the slave expects one command byte, and answers with four bytes of data, that's a 5-byte transfer, the slave will ignore the last 4 bytes, the master should ignore the first one.
A very simple transfer function would be
void SPIx_Transfer(uint8_t *outp, uint8_t *inp, int count) {
while(count--) {
while(!(SPIx->SR & SPI_SR_TXE))
;
*(volatile uint8_t *)&SPIx->DR = *outp++;
while(!(SPIx->SR & SPI_SR_RXNE))
;
*inp++ = *(volatile uint8_t *)&SPIx->DR;
}
}
It can be further optimized when needed, by making use of the SPI fifo, interleaving writes and reads so that the transmitter is always kept busy.
If speed is critical, don't use generalized functions, or make sure they can be inlined when you do. Use a compiler with link-time optimization enabled, and optimize for speed (quite obviously).
You can use HAL_SPI_TransmitReceive(&hspi2, ReadAddr, pBuffer, 1 + 4, HAL_MAX_DELAY); instead of a HAL_SPI_Transmit and a HAL_SPI_Receive. This will avoid the time between transmit and receive.
You can also try changing compilation settings to optimize the speed.
You can also check the accelerometer's datasheet, may be you can read all the buffer with a single frame, something lie this:
HAL_SPI_TransmitReceive(&hspi2, ReadAddr, pBuffer, 1 + (4 * numOfSamples), HAL_MAX_DELAY);
What worked for me:
Read SPI registers directly
Optimize your function for speed
For example function (code); See solution by “JElli.1” in ST- Community >>
ST Community answer
I have configured a UART to receive in DMA mode where the size of the buffer is around 64 bytes. So, basically, the HAL_UART_RxCpltCallback() DMA receive complete interrupt will only fire when 64 chars are received.
Is there a way in STM32 through which I can configure a timeout for DMA Rx where when the buffer is only partially filled (i.e. less than 64 chars are received) and we don't receive anymore chars for a specified timeout, the DMA will then raise the same HAL_UART_RxCpltCallback() based interrupt to let the consumer consume whatever partial data is currently received on the UART?
You can use the UART Idle detection interrupt in parallel to the DMA interrupt.
I have used this multiple times with ST32F0xx processors and it is working perfectly.
There Idle detection should be available on F4 and F7 processors too.
There are some tutorials in the internet which target your problem and also provide the solution with the Idle detection.
E.g. check out this one this one.
It's easy but you have to use USART receiver timeout interrupt instead.
in order to get a count of transferred bytes, you can use DMA_CNDTRx or DMA_SxNDTR register (name different for STM family, where x - channel number ).
This register decrements after each DMA transfer. Once the transfer is completed, this register can either stay at zero or be reloaded automatically by the value previously programmed if the channel is configured in autoreload mode.
Unfortunately, STM HAL doesn't provide API, you should implement it yourself.
I'm using an Atmel SAM3S MCU, and their ASF stuff can do I2C (they call it TWI) communications. That's fine, except it's taking too much time from my main loop.
So, I'd like to be able to spark off a DMA transfer to read the data from the I2C device. However, all the docs say you can't turn on TX and RX simultaneously on a half-duplex device like TWI. The docs do show that it has a Peripheral DMA Controller (PDC) register section in the TWI registers, but I can't find any PDC examples, except for the USART, which is full duplex.
The only thing I can think of to try is to set TX section, and the next-RX section, and hope that it automatically enables RX after the TX is done.
Has anyone out there used DMA for an I2C read on the SAM3S? If so, could you point me to some docs or examples?
I'm not familiar with the particular part, however I would suggest that for many common usage patterns your best bet would probably be to only use DMA to handle multi-byte sequences of data. Most I2C peripherals allow data to be read out by performing a start with a "write" address byte, and, if that is acknowledged, sending out an address or other information about what data is desired. This is followed by a restart and a "read" address byte. If that is acknowledged, one may then perform all but one of the byte reads with the "ack" flag set. When that is finished, ask for the final byte to be read with the "ack" flag clear.
I'm not sure whether it would be worthwhile to use the DMA controller to clock out the bytes of the requested address, but probably not worthwhile to try to use it to clock out the first byte of the read command.