I had use arduino uno sch to build my own board with other sensor on board.
after putting boot loader and blink and serial sch . I found it working slow delay of 100 act as 1000.
4800 act as 9600
I thought my assembler had putted the wrong crystal(smd). Now I want to test the circuit with internal oscillator. but hard to find how to make it happen.
So two questions
The ATmega328p comes from the factory with the configuration fuses set for internal clock and an initial clock pre-scale of 8. That makes it run at 1 MHz. You are expected to use "Burn Bootloader" to set the fuses and load the Arduino bootloader.
Are you using an 8 MHz crystal or 16 MHz crystal?
That what I am not sure of, assembler may had putted wrong crystal. it was suppose to use 16Mhz
Can you name out the fuse in bords.txt which allow me to use external oscillator
johnwasser, very noob here...
how would your answer differ if it were 8mHz or if it were 16 mHz?
grint:
how would your answer differ if it were 8mHz or if it were 16 mHz?
16 MHz: Burn an Arduino UNO bootloader
8 MHz: Burn an Arduino Pro or Pro Mini ATmega328 (3.3V, 8 MHz) bootloader
Any other answer: Good luck. In most cases 20 MHz will work but you need a custom boards.txt file. Any other value will get you millis() and micros() timers that are going to be off in various directions.
There is no standard Arduino configuration that uses and ATmega328P and the internal clock. The Lilypad Arduino with ATmega168 seems to use the internal clock. To use it you would want to install a custom boards.txt file.
8 MHz operation has advantages.
It allows 3.3V operation. Connects direct to 3.3V devices like SD cards and adapter sleeves.
It frees 2 pins, Port B 6 and 7, opening a full 8 bit port on the 328P.
Running on internal clock is one of the options Nick Gammon's bootloader burner does:
embeddednerd:
That what I am not sure of, assembler may had putted wrong crystal. it was suppose to use 16Mhz
Look at the crystal and see, then - almost all crystals will have the frequency marked on it, or a part number with the frequency in it.
You should be able to tell exactly by blink if you have a good clock. Run a 1 second blink sketch for 30 real seconds and see if you get 30 or 15. There's you clock indicator.