Questions tagged [8051]

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

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8051 to I2C backpack/4 bit LCD Byte Construct Probelms

Been feverishly writing bit bang code in assembly for this I2C backpack/4 bit LCD and dont quite understand the binary constructs I need to display text. Im trying to learn this the real way, not the ...
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57 views

What is a page in 8051 microprocessor?

https://www.hobbyprojects.com/8051_tutorial/acall_absolute_call.html I was learning about acall on the above website, but then came across the term page. What exactly is a page?
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How to program CH559 to use one USB as master the second one as slave?

I have found a video in youtube which uses CH559 to connect a normal mouse/keyboard or both at the same time in order to make inputs to arduino. These inputs can be visualized from the OLED ...
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59 views

How these timer values are derived?

I have a 8051 micro controller ,it has timer0,1,2,3 with different modes. in timer0,mode0, i got a sample code (as shown below). datasheet 8051 from that code ...
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57 views

In asynchronous communication how is the frequency same but clocks of both devices different?

Am currently studying 8051 microcontroller and in the course the lecturer told that in communication the frequencies of sender and receiver should be same else they will get different bits of data at ...
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54 views

What happens at hardware level when we feed a code? [duplicate]

I wanted to know what hardware is installed in 8051 such that whenever i write a program it accepts it and execute it. My query is what happens at the hardware level whenever i feed a program to 8051.
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37 views

proteus just stopped simulating on firmware projects

I am a student of computer engineering I was working on my assignments and project on proteus using microcontroller 8051 and using Keil micro vision compiler for c coding. I was working on my projects ...
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93 views

Two switches and two LEDs using 8051

I am trying to work around a circuit and my requirement is as follows: - There are two inputs and two outputs. Each input controls an individual led. I am writing a code for this requirement using a ...
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42 views

minimizing waiting time for 8051 port state

I made myself a project with standard 8051 microcontrollers (AT89S52 and AT89C4051) and will be making more with the same due to price and availability. When data is being sent from one GPIO pin from ...
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45 views

ENC28j60 ethernet interfacing with efm8lb1 help needed

I am a newbie to ethernet controller. I went through ENC28j60 documentation But I couldn't find a proper example similar to my project. EFM8LB1 will read some sensor data (for example sensor data '...
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153 views

How can I code in a buzzer while using a 7-segment in an 8051

I'm currently working on a small queuing system where whenever someone presses a button (which I have linked to INT0), my 8051 would increase the register and would display a higher number on the dual ...
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67 views

Why does this driver not have a load resistor?

Im trying to drive a motor with this kind of circuit since my micro is an old 8051. The voltage I use is 5V and PowerV is also 5V. I also have a 56 ohm 1/2 watt resistor in series with my motor ...
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37 views

Weird error pattern on CC2541, the 8051 core

I am playing with the debug interface on the TI CC2541. It seems to be working fine, seeing correct chip ID etc. The interface has a DEBUG_INSTR command that lets you submit and execute an ...
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59 views

Grounding GPIO pins during 8051 programming

I'm trying to make a programmer for the 8051 microcontroller IC's, specifically the AT89C2051. I saw a circuit online (the blowit programmer) in which the unused GPIO pins are left floating. When the ...
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49 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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41 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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97 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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952 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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50 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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80 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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123 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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48 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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51 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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269 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 pin 3 is touched How can I detect it? A ...
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296 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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265 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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680 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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161 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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107 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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104 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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42 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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59 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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43 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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47 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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49 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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37 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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99 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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178 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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953 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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254 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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37 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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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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279 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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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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365 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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238 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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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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95 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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205 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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