[En-Nut-Discussion] Could not enter programming mode

[Daniel]

Andre Riesberg schrieb:
> Daniel wrote:
>
>   
>> Hi.
>>
>> While I was programming my Ethernut 1.3 with stk500.exe, I had connected 
>> SCK (SPI Bus Serial Clock) to GND. After that I read, that I must not do 
>> that.
>> Now stk500.exe tells me, that the controller "Could not enter 
>> programming mode".
>>
>> Any advise how to fix it up?
>>
>> Thanks,
>> Daniel
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>> http://lists.egnite.de/mailman/listinfo/en-nut-discussion
>>
>>
>>  
>>
>>     
> Hi Daniel,
>
> do you pull the SCK signal to GND only on the programmer or on cpu or on 
> both?
>
> Do you have disconnected all power supplys and start again?
>
> Please make some tests:
> First, disconnect programmer and CPU.
>
> - Check the SCK signal at the programmer: In normal condition (no 
> programming) the signal must be on high level.
> - Check the SCK signal at the CPU board. Normally you see a low level. 
> With a 10k resistor to +5V you can pull this signal to high level.
> - With still disconnected board try to start programming (I use 
> avrdude). With a scope you can see (for a short time) a lot of pulse on 
> the SCK line.
>
> Does this work?
>
> Greeting
> Andre
>
>
>
>
>
>
> _______________________________________________
> http://lists.egnite.de/mailman/listinfo/en-nut-discussion
>
>   

Hi Andre, thanks for the answer.

Here are the results of the tests you mentioned:

- SP Duo 2 Programmer, only supported with Vcc & GND, not connected to 
CPU: SCK (PB1) is low
    When I start programming, I see a short low voltage at SCK. 
Unfortunately I doesn't have a scope, only a voltmeter.
    You say, the signal must be on high level. It's low. But I can 
program my second Ethernut with this SP Duo without problems.

- CPU, not connected with SP Duo 2: SCK (PB1) is low
    Should I try to pull the SCK line high, when I connect the 
programmer to the CPU?


Daniel