RFID and USART atmega8

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#1
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Hello, i'm doing a school proyect that  includes a access control with RFID. We are using SPI for comunicated the atmega 8 with it, also we are using a nextion screen with the usart. When i connect all the circuit the RFID doesn't read the tags, but when i disconnect the screen of the atmega8 and turn on the circuit the RFID read the tags and i don't know why. 

 

 

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We don't know why either. It could be a hardware or a software problem - or both. Since you have not shown us the hardware, we cannot comment on that. Think of how you could formulate some tests to narrow down the problem. 

My first thought would be power supply. Measure this with and without the nextion attached.

 

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these are the connections

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YOu do not show what the Vcc and AVcc  or the grounds of the AVR are connected to.  I see no filter caps on the AVR either.  Also.  Nextion screens are power hungry.  What is the Main power supply capable of providing in amps/wattage?

 

Jim

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

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Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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The avcc isn't connected. Vcc and Gnd are connected in the hi link power supply. The power supply is 5v and 0.6A. I proved other program with out using the eeprom and it works, the problem is when I changed the program

Last Edited: Sat. May 23, 2020 - 04:08 AM
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Read the datasheet - avcc must be connected. You also need bypass capacitors. Ignore this and expect problems.
Your fault report didn’t say anything about changing the program or eeprom.

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See here...

 

https://www.avrfreaks.net/forum/...

 

...this applies to ALL AVRs.

#1 Hardware Problem? https://www.avrfreaks.net/forum/...

#2 Hardware Problem? Read AVR042.

#3 All grounds are not created equal

#4 Have you proved your chip is running at xxMHz?

#5 "If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand."

Last Edited: Sat. May 23, 2020 - 07:16 AM
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Isbel24 wrote:
The power supply is 5v and 0.6A

 

Too small.  You will want at least a 1 amp supply

 

Jim

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user