Yes! When you configure the fuses to make the controller run from an external clock, you also need that external clock for reprogramming.
It is important to notice that I tested this with an Arduino configured as ISP (In circuit Serial Programmer), which does not attempt to provide an external clock to the device that is being programmed. Other programmers may do this, but that would depend on the programmer. ISP is most common way of programming these devices, but there are other programmers too. Fact is that the device in itself needs an external clock. Unsure for a parallel programmer. A High Voltage programmer can do without an external clock.
I didn't test this with an ATmega, but rather with an ATtiny45, but both AVR's are very similar in these aspects.
This is what I did:
- I wrote a small program to output a 1kHz square wave output (listing below);
- I selected 2MHz clock and programmed
.low = 0x61 Notice that the fuse settings may be controller specific, so this is the setting for ATtiny45;
- The controller outputs a frequency of 1kHz, as expected;
- I selected 1.8432MHz for clock and programmed
.low = 0xe0;
- Output frequency dropped to 0Hz until I connected the oscillator, then it jumped up to 1kHz, again as expected;
- I detached the external oscillator (output: 0Hz);
- Tried programming the device, resulting in:
avrdude: Device signature = 0xffffff
avrdude: Yikes! Invalid device signature.
Double check connections and try again, or use -F to override this check.
- I reattached the external oscillator and programed the device for 2MHz the following result:
avrdude done. Thank you.
- and of course the ouput was back at 1kHz.
So in conclusion:
If you program the fuses for using an external clock, then you also need an external clock to program the device.
/*
(c) copyright 2013 by J.P. Hendrix
*/
#include <avr/io.h>
#include <util/delay.h>
#define _BS(bit) ( 1 << ( bit ) )
#define _BC(bit) ( 0 << ( bit ) )
/*
ATtiny45
pin function name ISP SPI XO I2C/TWI comparator ADC pin chg
1 !RESET PB5 ADC0 PCINT5 dW
2 extOscPin PB3 XTAL1 CLKI !OC1B ADC3 PCINT3
3 PB4 XTAL2 CLKO OC1B ADC2 PCINT4
4 GND GND
5 PB0 MOSI DI SDA AIN0 OC0A !OC1A AREF PCINT0
6 outputPin PB1 MISO DO AIN1 OC0B OC1A PCINT1
7 PB2 SCK USCK SCL T0 ADC1 PCINT2 INT0
8 VCC VCC
*/
const uint8_t outputPin = _BS( PB1 );
const uint8_t extOscPin = _BS( PB3 );
#ifdef F_CPU
#if ( F_CPU == 1000000 )
// 1MHz
FUSES = { .low = LFUSE_DEFAULT , .high = HFUSE_DEFAULT , .extended = EFUSE_DEFAULT , };
#elif ( F_CPU == 1600000 )
// 1.6MHz => ATtiny15 Compatibilty Mode
#warn "ATtiny15 Compatibility Mode changes Timer1 behaviour!"
FUSES = { .low = 0x63 , .high = HFUSE_DEFAULT , .extended = EFUSE_DEFAULT , };
#elif ( F_CPU == 2000000 )
// 2MHz
FUSES = { .low = 0x61 , .high = HFUSE_DEFAULT , .extended = EFUSE_DEFAULT , };
#elif ( F_CPU == 6400000 )
// 6.4MHz => ATtiny15 Compatibility Mode
#warn "ATtiny15 Compatibility Mode changes Timer1 behaviour!"
FUSES = { .low = 0xe3 , .high = HFUSE_DEFAULT , .extended = EFUSE_DEFAULT , };
#elif ( F_CPU == 8000000 )
// 8MHz
FUSES = { .low = 0xe2 , .high = HFUSE_DEFAULT , .extended = EFUSE_DEFAULT , };
#elif ( F_CPU == 16000000 )
// 16MHz
FUSES = { .low = 0xe1 , .high = HFUSE_DEFAULT , .extended = EFUSE_DEFAULT , };
#else
// #error "F_CPU setting not recognized."
// External oscillator selected
FUSES = { .low = 0xe0 , .high = HFUSE_DEFAULT , .extended = EFUSE_DEFAULT , };
#endif
#else
#error "F_CPU not defined."
#endif
void setup( void ) { // Initialize all hardware
DDRB = outputPin; // Data Direction Register Port B
}
int main( void ) {
setup(); // Initialize the hardware
while ( 1 ) {
_delay_us( 500 );
PORTB ^= outputPin;
}
}
I don't think you're sending the ROM Command after you have initialized the bus. According to the datasheet, page 4:
The sequence for accessing the DS2401 via the 1-Wire port is as follows:
- Initialization
- ROM Function Command
- Read Data
The command you probably want is
Read ROM [33h] or [0Fh]
Also, are you really running at 1MHz, as stated in the auto-comment? Timing could also be the cause of these problems.
Best Answer
Yes, of course you can replace your DS2410 by something else that behave like the DS2410.
Use another AtMega32, because you seem familiar with it, and connect one IO of it to the 1-wire bus.
Remember than the 1-wire bus requires open-drain masters and slaves. Thus you will control your 1-wire pin by switching between output low and input instead of output low and output high.
In all case you will have to write a custom firmware for that additional AtMega to instruct it to behave like a DS2410.