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Questions tagged [8051]

The "8051" is a (still) very popular chip in the Intel MCS-51 micro controller series.

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21 views

interrupt-on-change on 8051 microcontroller

I am trying to read the speed or number of rotations pulses of a self-made encoder motor. I am using an AT89C52 microcontroller. It gives external interrupt on rising or falling edge. How can I ...
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16 views

Chaging EA/VPP by software on Intel MCS-51/8051

I'm designing a circuit that uses the combined Program/Data bus from Intel MSC-51 as advantage. By the MCS-51 specification it has an internal 4K ROM and a EA/VPP pin that if set to high will access ...
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51 views

Converting “MPR121 capacitive keyboard” sensor filter data into capacitance values?

The project that I'm working on, the MPR121 capacitive touch sensing keyboard connected with a 8051 microcontroller, my first intention when I started implementing the project was to measure the ...
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467 views

8 channel quiz buzzer circuit using 8051 microcontroller

Project: 8 channel quiz buzzer circuit using 8051 microcontroller from this site. For the first candidate who presses their button, their number will show on the 7-segment display and the buzzer will ...
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37 views

ACK even for the not existing register, I2C problem!

I'm implementing this project with MPR121 keyboard communicating with 8051 via I2C before I get further into the program I wanted to know whether the sensor is communicating with the board, giving the ...
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36 views

8051 Open Drain Operation

While studying I ended up finding this question. Write the value (in hex) of the P1 after the execution of the code below. ...
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39 views

Assembler program showing ACK even with the wrong slave address, I2C code problem!

I have this project communicating MPR121 capacitive touch sensing keyboard with 8051 microcontroller, with some references I've implemented some I2C code for serial communication between master and ...
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1answer
45 views

How to check the flow of assembler instructions execution?

I'm creating a project that uses I2C serial communication in assembler and I'm having some issues transmitting data and receiving back so I thought I should somehow debug the whole program, besides ...
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37 views

Check if the slave is receiving data from microcontroller and transmitting back successfully, I2C?

I have this project where I have to communicate MPR121 touch sensor keyboard with 8051 microcontroller via I2C, I've implemented the code and when I execute it I don't really know whether slave is ...
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2answers
107 views

How to check whether a byte of 8 bits contains 1, assembler 8051?

I need to know how to check whether a byte contains a 1 for touch status in a MPR121 project, so if: 00000010 then pin 2 is touched 00000100 then 3 is touched, how can i know it? A set bit means that ...
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80 views

8051 microcontroller problem to find execution time of part1 for a given code

For the below mentioned 8051 assembly code: Time elapse: MOV R0,#100 Part 1 \$ \quad \, \, \,\,\$ : MOV R1,#50 Part 2 \$ \quad \, \, \,\,\$ : MOV R2,#248 Part 3 \$ \quad \, \, \,\,...
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55 views

TMOD value for timer 1 in mode 0 in 8051 microcontroller

What will be result of this statement: MOV TMOD,#00H Will it set it to timer 0 in mode 0 or to timer 1 in mode 0? Other statements like: ...
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189 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 ...
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74 views

What is the XTAL clock used for in an 8051 microntroller?

I'm trying to design an 8051 microcontroller circuit which uses timers/counters, and the circuit I'm using for inspiration uses a clock generated using the XTAL1 and XTAL2 pins of the IC, shown in the ...
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1answer
41 views

Reset MCU with a 1-0 button

I am working on a silabs C8051 MCU. It has a sleep mode which should be woken up by a reset. The mcu should start working (wake up from sleep) when the button in connected to Ground (Otherwise it is ...
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61 views

old 80C31 circuit not working. EPROM data retention issue?

I have an old piece of pro-audio gear in for repair. It dates from 1990. It was a fairly high-end piece of gear at the time and still has some value so it is worth repairing. But the symptoms I see ...
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18 views

Checking HM-TRP radio adapter for initial data

I have several HM-TRP radio adapters (consisting of the HM-TRP chip with a female header connected to it) of the same version. I tested it in a mini circuit where the PC does direct I/O with the HM-...
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28 views

Can 8051's ALE pin be equivalent to ground?

I want to add another port to the 8051 and I plan to do so by connecting port 2 (pins 21 - 28 of the 8051) to the Q inputs (pins 2 - 9) of an edge-triggered latch (74HC574). I will also connect the ...
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30 views

CC2530: adapting AVR/pgmspace.h for Zigbee

Goal: Adapt ENC28J60 codes written for ATMega328p (http://tuxgraphics.org/electronics/201204/embedded-ethernet-client.shtml) for CC2530. Problem: No equivalent library for AVR/pgmspace.h available ...
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47 views

minimalist serial port addon to a basic 8052

Currently I have two microcontrollers connected to each other so that I have two serial ports. One to the PC and one to a wireless radio module. Now I'm considering replacing one microcontroller with ...
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28 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, ...
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1answer
41 views

Byte-Banging 2 8051's using port addresses

Currently I have two microcontrollers setup in which entire ports are connected to each other (P1.1 connected to P1.1, P1.2 connected to P1.2, etc). I also have two pairs of extra GPIO pins connected ...
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25 views

Can standard 8051 timer 1 and timer 0 be available to programmer when serial mode 1 is used?

The micro is an AT89C4051. It allows two timers and a serial port interrupt. Currently, I set things up so that if any kind of data is received on the serial port, it just is loaded into memory by ...
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47 views

Do some microcontrollers require data to be loaded in temporary memory before programming?

When I programmed the AT89Cx051 series of microcontrollers, I didn't have to use special memory to program the data, but now even though I'm following the instructions in the datasheet (found from ...
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32 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 ...
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2answers
91 views

Is it better on two closely connected microcontrollers to send nibbles with an ack or a byte with a delay for an ack?

I'm trying to figure out the best approach to transfer high-speed data one way between two microcontrollers (with their own crystals of the same speed) of the same variety (between AT89C4051 and ...
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1answer
130 views

8051 program not processing keypad matrix correctly

I made myself a small PCB (measuring about 6cm by 5cm). This is what is supposed to happen: Upon power-up, the LED goes red to indicate that the unit is ready for input. I then press any key down (...
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2answers
382 views

How to program 89C52

I am new to this site. I am now working on microcontrollers. I successfully burnt hex file to 89S52 using arduino as a programmer. But I want to program 89C52 as this is the cheapest atmel ...
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3answers
137 views

Why do we need to declare ports as input/output?

I am writing code in assembly language (AT89s51). When I see a standard program, the ports are typically defined as inputs or outputs. But, without defining them it seems to work fine. How is this ...
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1answer
24 views

Calculating required delay before pin value is recognized in 8051

I looked at the following in hopes my question will be answered: can we use 8051 pin as Input and output at a time? But the answer was vague. It stated: "though there is a 'strong' source ...
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56 views

8051's PCA Interference/Problem

I am using a CD4040 to divide a oscillator frequency and reading its period using PCA. The problem is I was using 3 oscillators, 120kHz, 70kHz and 30kHz and dividing it by 32. The problem is, when I ...
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426 views

Servo motor interfacing with 8051 by assembly language

I know the principles of servo motor and programming it, I already done it with FPGA and adjusted the PWM like I wanted. But with 8051 assembly, I can't do the PWM or generate the 20 ms for the motors....
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239 views

how to create a hex file in keil?

I want to programme at89s52 micro controller...using Keil u5. I searched on youtube googled it tried everything but cannot see the hex file. it says creating a hex file/location but there are no hex ...
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613 views

why capacitors are used with crystal oscillator?

I want to learn 8051 programming so I begin from hardware in which crystal oscillator is connected with capacitors. can anyone please explain why capacitors are used and why those 22pF? how they ...
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2answers
246 views

8051 baud rate calculator using 16-bit timer for software UART timing

I'm making a project in which pulsed laser beam data is sensed through many optical sensors (one sensor per port pin), so essentially, I'm going to be making 4 UARTs to sense this. Currently I am ...
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158 views

direct ac mains to MCU pin for zero crossing detection

to detect Zero Crossing of ac mains, can i connect an EFM8 pin configured as input directly to 220V ac via a resistor?
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3answers
893 views

how to detect power failure and make micro-controller save data in EEPROM

I am using Arduino nano for a project in which I have on a counter which is continuously increasing. And I want to retain count after a power failure. Data is changing more frequently so storing it ...
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1answer
85 views

I2C Communication to the Matlab from Sensor board(8051 µC)

I like to connect my board to Matlab through I2C communication(I2C-USB cable). Is there any library or example scripts in matlab to do it? What are the procedure to do it. for example, I connected ...
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2answers
186 views

Program counter goes to the end of code and 8051 Restarts

I have an 8051 MCU which I use keil to program it with C. My problem is that the micro-controller restarts at the end of some functions while they should return. Using a debugger I tried to check it ...
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117 views

Microcontroller is being restarted on function return [duplicate]

I have 8051 MCU and I use keil to program it with C. But in some functions when the function ends and it gets to the return line the MCU is restated. For example a piece of my code is ...
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132 views

8051 programmer not working when laptop lid removed despite suggestions in comments

UPDATE I took a suggestion of disconnecting my external monitor from my laptop and the results were the same. What I did notice however is that the AT89S52 chip always reports the correct signature ...
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1answer
73 views

8051 MCU with fast entry to ISR implementation

I'm developing a custom protocol processing device based on MCU. My protocol is somewhat similar to I2C and uses bit-banging instead of hardware implementation. I've done a prototype based on ...
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1answer
86 views

Converting negative numbers to hexadecimal number system

I was programming in 8051 and I faced this problem I had to convert the number -10000 to hexadecimal ( 2 bytes) the answer is 0D8h = #HIGH(-10000) 0F0h =LOW (-10000) but how the answer was found /...
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2answers
287 views

Error handling strings in a 8051

I am using a Texas Instruments CC1110, which is based on the 8051 microcontroller. I'm programming it using the IAR Embedded Workbench. I have written a function named ...
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61 views

8051 Nested Init Functions In C Source Files

When programming in C, I usually like to adhere to the convention of keeping functions short and readable, especially main(). I'm updating some 8051 code, and I've noticed a previous engineer has ...
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1answer
57 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 ...
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1answer
223 views

Simpler code than bit banging to get multiple serial hardware working with 8051

I created a circuit like the following: I have sub-circuits that all take serial data as input and do miscellaneous processing with it. Most of the sub-circuits are just light displays. I want to ...
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4answers
1k views

433 MHz RF noise problems

I know this is kind of a noob question. I am trying to establish a wireless communication between two 8051 microcontrollers using a 433 MHz RF module. But since 433 MHz is a quite noisy frequency, the ...
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0answers
180 views

interfacing max30100 to 8051(I2C Communication Protocol)

I'm trying to interface heart beat sensor max30100 to 8051 for this purpose I should use i2c protocol. I'm using the following code for that but the sensor doesn't work even though i do the ...
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143 views

An analog switch controlled by digital logic

I am trying to control the movement of a remote controlled car by using a 8051 microcontroller. In the remote controller circuit there are four push buttons(forward, backward, left, right). I need to ...