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1answer
97 views

Why does my Atmega328 clock seem to be off by a factor of 2?

I have an Atmega328 chip I am trying to debug. I have a sketch that blinks an LED and echoes back things received over the RX/TX pins. I am using the "Import Arduino Sketch" feature in Atmel Studio 7. ...
1
vote
1answer
54 views

RCC clock freq in STM32F103

If I select internal clock source to run my TIM3 in TM32F103 (TIMxCLK from RCC) as shown in the attached picture: CK_INT Then how to find out what is the freq of this clock? I am using External ...
1
vote
3answers
111 views

Is there a low voltage LED alternative?

I am trying to create a tiny little watch that is supposed to run off a coin cell (because it is so tiny) and basically just a microcontroller with a 30ppm 1Mhz oscillator that counts upwards. The ...
0
votes
1answer
67 views

MASTER Clock output from one micro to another vs independent clock src

I have a Small STM32 Nucleo board where the on-board ST-Link debugger has an 8mhz crystal for the debugging microcontroller. That microcontroller is set up to output its MASTER clock, in other words ...
1
vote
3answers
451 views

555 Clock Circuit - how to choose resistor value? [closed]

I need to design a 555 clock circuit to output a clock pulse of a specific frequency. The circuit I'm using is this one (from here): I've used this circuit before and it works fine but the website ...
0
votes
1answer
97 views

Cascade shift registers driven by single-cycle microcontroller

I'm trying to make a unit in which 4 digits can be updated in a small amount of time from a single-cycle microcontroller (preferably all digits updated within 5uS) My circuit is setup in the ...
0
votes
2answers
62 views

Can I use MCU's internal oscillator when communicating with GPS and cellular modules?

Can I use MCU's internal oscillator when communicating with GPS and cellular modules? I want to avoid connecting external crystals for the MCU since they generate noise, extra components, extra costs, ...
0
votes
1answer
38 views

Bidirectional data bus divided into nibbles not returning correct data - 8051

Since I have 10 I/O lines connected between two microcontrollers (AT89C4051 + AT89S52), I am trying to get away with elegant data transfer. Instead of spending months redoing an entire circuit board, ...
2
votes
1answer
144 views

GPSDO control algorithm

I am currently building my own GPS disciplined oscillator. I have a OCXO which is used as clock source for a microcontroller and one of its counters, and the 1PPS signal from the GPS module is ...
2
votes
1answer
669 views

STM32L0 - Delay in microseconds

I am using a B-L072Z-LRWAN1 board (which has a STM32L072 MCU) and I want to get data from a DHT11 sensor. To achieve this, I need a microseconds delay which I am not able to obtain. The libraries ...
2
votes
1answer
255 views

Separate GND-plane for microcontroller crystal resonator

1.  Background info I'm designing a board for an STM32F767ZI microcontroller. This microcontroller has a primary oscillator for the SYSCLK (overall system ...
0
votes
1answer
996 views

STM32 F4 max GPIO toggle frequency [duplicate]

I just started using the STM32 F401VC Discovery Evaluation board and I'm trying to get the maximum GPIO toggling frequency without assambler. So my tought process is following: The code I was ...
0
votes
0answers
35 views

Can this circuit produce 0, 5 and 12 volts in fixed increments for the AT89LP4052?

Due to the speed requirements of my project, I'm looking at replacing the AT89C4051 with an AT89LP4052 with some code modifications since it offers double the memory and 6x the speed for the same ...
12
votes
3answers
3k views

How do processors control their clock speed?

I recently came across an STM processor with 2 oscillators on the circuit - I suppose one for high-speed operation and the other for low power. For something like a desktop processor where the clock ...
0
votes
0answers
58 views

resistor at external clock source line [duplicate]

im reading a arm based mcu board schematic and there is 100R resistor (R30) at external 25MHz oscillator source. What is the main reason of using serial resistor at clock line ?
0
votes
0answers
40 views

Faster 8051 not taking the slower 8051 pin status correctly

I'm trying to do a rather simple data transaction between two 8051 microcontrollers using a variant of the SPI protocol. The large one is a slave and the small one is a master. The documentation for ...
0
votes
1answer
59 views

Can this circuit validate AT89Cx051 micro if best valued components are used?

This is a circuit I made in an attempt to validate that the 20-pin microcontroller is an AT89Cx051. and the correct LED will turn on based on how much ram the chip has. While the first step is ...
1
vote
1answer
75 views

Is it possible to connect eight digital inputs to a digital output? [closed]

Can eight digital inputs (at 20-Mhz) output to 160-Mhz? Does a multiplexer work for this? Thanks for your answers.
0
votes
1answer
92 views

Is this machine code insufficient to chip timing?

I'm having trouble performing basic communication between two IC's. and AT89S52 and an AT89C4051. Both are connected using 6 GPIO pins of which 4 of them on each microcontroller are high nibbles of ...
2
votes
3answers
3k views

How to configure Atmel SAM D20 for internal 48MHz clock source?

I try to run a Atmel SAM D20 MCU at 48MHz using the internal oscillator (OCM8M) and the digital frequency locked loop (DFLL48M). All I achieve is a deadlock of the processor, even I use a simple "...
1
vote
3answers
1k views

Do I need a crystal to for the Atmel SAM D20 MCU to Run at 48 MHz?

I am working on a very small device and would like to use the Atmel SAM D20 as MCU (this variant ATSAMD20E16). Reading the data sheet, there is only one point I do not find clearly spelled out: Do I ...
-1
votes
1answer
124 views

STM32F4 OC Clock Jitter Problem [duplicate]

I am using STM32CubeMX to configure an STM32F4 to output a clock signal using Timer 3, Channel 4 on PC9. I have read in the datasheet PLL section that jitter shouldn't be more than 15ps RMS but I am ...
1
vote
0answers
199 views

STM32F4 OC Clock Jitter

I am using STM32CubeMX to configure an STM32F4 to output a clock signal using Timer 3, Channel 4 on PC9. I have read in the datasheet PLL section that jitter shouldn't be more than 15ps RMS but I am ...
0
votes
1answer
249 views

Configure UCSCTL0 register MSP430F5529

First off: I'm brand new to microcontroller development, so please forgive me for the simple question. I'm trying to learn for my FIRST robotics team so we can use the MSP430 to handle some extra ...
0
votes
2answers
1k views

Timer configuration on STM32F4

I'm trying to configure the timer3 to have a frequency of 1KHz, without success. Here's my configurations: System Clock: ...
2
votes
1answer
859 views

Connect STM32 Ethernet to PHY - clock signal

I want to connect MAC available on STM32F745 to KSZ8041FTL (PHY) via RMII. I will clock PHY from external 50MHz clock generator, connecting clock to the REFCLK input of PHY. But what about STM32? ...
2
votes
1answer
377 views

Understanding PCIE and FPGA clock “magic”

I've been trying to understand how PCIE clocking works when it comes to connecting an FPGA to a PCIE slot in a motherboard. Looking at page 12 of this schematic for exampe: https://www.xilinx.com/...
-3
votes
1answer
72 views

analyzing real time data [closed]

I want to digitize a 10MhZ signal to 16 or 32 bits, then multiple that number with about 200 different complex numbers then keep a running sum of each of the 200 results. If I don't do this in real ...
1
vote
1answer
653 views

Clocks, Processors and Timers on a MCU

So i am going through this excellent book Patterns for Time-Triggered Embedded Systems and have a question regarding calculating values for hardware timers precisely. See "Hardware Delay" pattern in ...
3
votes
3answers
392 views

Count cycles from oscillator clock to get time

first time on stackexchange, hope I'm in the right place. I am working on a project where I need to timestamp an event (which will be detected from an electrical pulse) down to a few tens of ...
1
vote
0answers
145 views

Can't get PIC16F1764 to run at 32 MHz INTOSC

I have a problem with a PIC microcontroller. I can't get it to run at 32 MHz. Via page 78 of it's datasheet (document number DS40001775B). The steps for selecting 32 MHz FOSC operation are clearly ...
3
votes
1answer
1k views

STM32F4 Timer accuracy and jitter

I'm trying to generate a 24MHz clock signal from the STM32F407 running at 168MHz. This signal would then be used to clock a USB hub IC (Microchip USB2513B). From the hub's datasheet, I learn that the ...
4
votes
2answers
664 views

What kind of external clock is needed for PIC32?

Nearly all PIC32 errata I have read (Item 41 - page 5) have the same issue - A crystal oscillator cannot be used as an input to the Primary Oscillator (OSC1/OSC2 pins). An internal oscillator ...
2
votes
1answer
569 views

PIC32MX can't get 80 MHz Clock from Internal RC OSC

I am using PIC32MX795F512L with the internal RC oscillator. By changing the settings of the config, I can get to 60 MHz max. But I can't get to 80 MHz. When I change the config for 80&#...
3
votes
2answers
274 views

Choosing crystal, strangely narrow requirements in MCU datasheet?

I am making a prototype using the Atmel ATSAM4S2B microcontroller, but I am having trouble choosing a crystal. I need a 12MHz crystal to use the integrated USB module. The problem is, in the ...
1
vote
1answer
246 views

Confusion with PIC32MX1XX/2xx datasheet information (clock source for USB)

Maybe there are some experienced "wolves", who could help out to clear out confusion about internal/external clock sources. Particularly, I got lost while reading PIC32 family reference manual, "...
4
votes
2answers
1k views

How to generate high frequency clock with high stability from a microcontroller?

I am using TivaC launchpad TM4C123G microcontroller, to generate a clock of 40 MHZ but I tested it on the oscilloscope and it doesn't look like a square wave it's more like a sinusoidal here is a ...
0
votes
1answer
1k views

Output 48MHz system clock on a GPIO pin other than MCO pin on STM32F030

I want to output the max 48MHz clock signal of STM32F030 to drive another subcircuit. The problem is the chip STM32F030F4P6 (TSSOP-20 package) I prefer to use a GPIO because the MCU doesn't have the ...
0
votes
1answer
775 views

Strange ADC sampling frequency / clock frequency on STM32F401 board

I use a timer to trigger ADC sampling on STM32F401, and the interrupt service routine of ADC will toggle a GPIO pin so that I can measure the ADC sampling frequency using an oscilloscope (which should ...
6
votes
0answers
813 views

Why is there a need of external clock even though MCUs can provide timing? [duplicate]

Why is there a need sometimes for an external crystal, even though the MCU have an internal oscillator? To give you an example, the Atmega328P used in Arduino Uno has an internal 8Mhz internal ...
31
votes
8answers
21k views

Why do Microcontrollers need a Clock

Why do instructions need to be processed at set time intervals (i.e. with the use of a clock)? Can't they be executed sequentially - immediately after the previous instruction has completed? An ...
1
vote
1answer
1k views

PIC 16F887 and the mysterious System Clock Select bit (SCS)

I'm using a PIC 16F887 and I'd like to use the internal oscillator HFINTOSC. To accomplish this, I set the IRCF 2:0 bits to 110 (4Mhz prescaler) and the FOSC 2:0 config bits to INTOSC. Now I should ...
5
votes
3answers
32k views

How to calculate the time of one single tick on microcontroller

I have been in Embedded system for 8 months. I have worked application part more compare with low level. I have basic questions on systems ticks, How to calculate the system tick of Timer, if I am ...
3
votes
1answer
399 views

What parts could be labeled XT and be near a Clock of a microcontroller

An ice cube maker stopped working with the symptom that the temperature cycles are getting shorter and shorter. I suspect that the microcontrollers clock is not working properly. I desoldered a part ...
3
votes
2answers
2k views

How to check frequency of MSP430 clock?

I'm working on a project in which an MSP430 is used to provide the timing for some stuff where accurate timing is important (it can be off by 10%, but not by 2x). This is driven by the timer A0 ...
2
votes
1answer
226 views

How can two separate devices send clock data to a shift register IC?

I'm using a microcontroller to clock a byte into a 74HC595 shift register and latch it. It then sends a signal to the other device which send 8 clock pulses when it is ready to receive the byte. So ...
0
votes
2answers
373 views

Why prescaler doesn't give 50% duty cycle pulse

I am new to embedded electronics. While reading the datasheet of ATmega328P, I saw this when timers and their timing diagrams were given... I wonder why clk/8 is not of 50% duty cycle...Please help ...
3
votes
3answers
2k views

What is the difference between processor clock and system clock?

In the TM4C123G Launchpad Workshop page 129, there is a note about power modes. This note differentiate between processor clock and system clock. So what is the difference between them ? Is this a ...
0
votes
2answers
325 views

Can we observe addresses, data and other signals on the microcomputer buses by an oscilloscope, a LED or even an ordinary DC voltmeter?

Microcomputers are dynamic devices that are synchronized by a clock oscillator. So the signals (E, R/W, CS, A15-A0, D7-D0...) appear on their buses only for parts of a microsecond and, as the buses ...
1
vote
1answer
3k views

Choosing between internal oscillator and external crystal- ATXMega32E5 [duplicate]

We are working with a modern microcontroller ATXMega32E5, from the ATMEL XMega family. Our aim is to use the UART of the controller for effective communication, with the speed of about 9600 or 4800 ...