This is a snap from the debug window in Keil for 8051 Microcontroller. I have done an Embedded C program that would take detect an external interrupt in any of the pins and execute an ISR.
When I tried to change the value of the pin, it showed up the error "You tried to change the port pin which is configured as output pin"
My doubt is that, what is the difference between P3 and Pins (as shown).
Related
I have developed a custom STM32L475 board with one GPIO pin wired up for synchronization along some other circuitry for the synchronization, unfortunately we decided to route the generated sinus signal from module to module.
This is not optimal so I want to optimize so it is not the sinus signal which is routed from master module to slave modules, but to just transfer a digital trigger to restart the generation of a full sine wave.
To do this I need to be able to setup the MCU's to use the one GPIO pin on each MCU as both output and trigger for a timer.
To do this without an update of the HW I need to be able to combine:
1. Using the 3 pins (one from each MCU) as open drain outputs as an AND gate, this works.
2. I know the GPIO pin can be used as external trigger, triggering on a negative edge.
The question is, is it possible to trig a timer of an output pin using only one GPIO pin, to make the MCU which finalizes its sine generation first trigger itself and the other MCU's, and if so, how?
Please note, it must use the level of the output pin itself, eventhough it is an outputpin.
I am a HW developer, learning to do firmware for our HW, so I am kind of new to software development, so I am using HAL, please be nice
STM32L475 allows to configure a GPIO in different modes that must be (exclusively) selected through the corresponding GPIOx_MODER register:1
(Digital) Input mode
General purpose output mode
Alternate function mode
Analog mode
The alternate function applied in Alternate function mode must also be selected exclusively, through the corresponding GPIOx_AFRL or GPIOx_AFRH register, resp.2
The trigger for an interrupt or timer is an alternate function, and the output of a (analogue or digital) signal is a (different) alternate function, too.
Therefore, I think there is no solution to the given problem based on peripheral configuration.
1
Reference Manual, Rev 7:
See
Section 8.5.1 for GPIO mode selection
Figures 23/24 in Section 8.4 for explanation
2
ibid.:
See
Section 8.5.9 for GPIO alternate function selection
Section 8.4.2 for explanation
I'm trying to interface 8x2 lcd using parallel interfacing[4 bit mode],
Display used - 8x2 lcd [PC 0802--A]
ST7066U--Dot Matrix LCD Controller/Driver
Since i'm trying to interface using GPIO pins, not using I2C or SPI
interface, and since no drivers are there for this particular MCU[LPC845],
I compared with lpc2148 MCU [lcd.c and lcd.h files], and have made the changes, but not able to write to the display.
And when checked the data/command signals in the oscilloscope, in data pins
I'm getting float voltages[i.e., for d4-D7] LOW signal on this pins, and
high signals on command pins[RS,RW,EN].
Kindly suggest me the process of writing the char/string to the display varies for ARM mcu?as i'm referring lpc2148 libraries.
Thank you
I have an STM32L051 and want to drive an external DAC (SPI).
For that I would like to use the feature, mentioned in the manual, to output the internal reference voltage to the PB1 pin of the STM32.
I use the STM32Cube HAL as a basis. However the examples of using the VREF are limited to internal use for ADCs and comparators.
If I understand correctly, I can use the CFGR3 register to both enable the VREF as well as connect it to the PB1. Using the Cube drivers, I can use the HAL_SYSCFG_VREFINT_OutputSelect(SYSCFG_VREFINT_OUT_PB1) function, but to enable it, I should use either HAL_ADCEx_EnableVREFINT() or HAL_COMPEx_EnableVREFINT(). The manual information on SEL_VREF_OUT indicates that ENBUF_VREFINT_ADC must be set.
Furthermore no mention is made about the configuration of the pin itself. Should I simply declare it as a DAC Pin? An ADC Pin?
Answer
It is as simple as
if ( HALD_ADCEx_EnableVREFINT() != HAL_OK )
{
Error_Handling();
}
HAL_SYSCFG_VREFINT_OutputSelect(SYSCFG_VREFINT_OUT_PB1);
And I can see the 1.22 V on the PB1 output.
It does not require further pin (GPIO) configuration.
Complications and justification for the question (can be skipped)
I had some issues with the board from out electronic dept. and thus switched to the STM32L053-Discovery board. The above solution did not work, and I kept seeing 0V on PB1 (or PB0).
I assumed that was due to some configuration missing. However, after some further tests, I actually found that on that Discovery board, both PB1 and PB0 are reserved for a sensor. By closing the SB23 bridge, I could use PB1 back to the GPIO, and thus see the reference voltage on the pin.
I've configured the timer 2 in CTC mode and to toggle the port pin on compare match (TCCR2A=0x42, TCCR2B=0x02, OCR2A=0x20) and have set DDR3 to output. Hence, according to the ATmega328P documentation (pages 158-163). OC2A (aka PB3) should toggle on each compare match. Unfortunately, I can't read the pin state at PORTB. Is this expected? I assumed, that even if a port is configured as output I can read the set value.
There were two problems:
In AVR Studio 4.18 I must not use the Simulator 1, because it has a bug for the timer 2 and hence can't toggle the port pin correctly. I needed to use Simulator 2 or AVR Studio 5.
I needed to read PINB instead of PORTB (though the toggling is an output operation).
I don't know about that specific microcontroller, but in some architectures you need at least a NOP between changing the port pin and the latch being updated (so you can read the change).
Also there is the maximum frequency a pin can be toggled at (many times slower than the microcontroller CPU clock). Be sure to not be over that frequency.
I am using EWARM IDE from IAR with an Olimex development board for the ARM STR712FR2, and a J-link JTAG debugger provided by IAR. For some reason, I can't seem to write to the UART TxBUFR register. I believe I have configured all the clocks and baud rate correctly. The datasheet says that when I write to the TxBUFR register, the UART is supposed to immediately start transmitting. I am running this in debug mode, and when I place a breakpoint right after I set the TxBUFR to a value, the register still shows 0x0000, unchanged.
The register value may not change or it may be write-only, have you checked to see if it is actually transmitting or not?
The UART_CR register resets to 0 which has some fields set to reserved values. Have you configured all the fields in here? ALso, as was mentioned, UART_TxBUFR is a write-only register, so you will not be able to read the value back.