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SD2IEC on a Plus 4?


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I've just bought an internal sd2iec for my Plus4.


Installed it and tried to load the FB16 program and it jst hangs saying 'searching for fb16'


I've installed these before with no problems in C64's and vic20s


I'm only getting 4.7v on the power lines on the sd2iec - could that be the problem?

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That’s what I thought.
Those sd2iec is slightly different to the ones I’ve had before. It came from retroguru.eu in Poland. It came with some extension wires, a 3pin LED and a push button. No instructions or links came with it at all.


I installed it the same way as any other computer and used pins 1&2 from the User port for power. I copied the software with the 2x firmware files and FB16 as normal onto an SD card formatted with fat16 (I also tried fat32, no difference) and it just hangs on ‘searching’

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I don't recall if BASIC 3.5 has any fancy disk commands but this old style should work:






If you omit the PRINT# on line 10, it will read the current status. On reset, E should be 73 with a string in E$. If no error, you get 0 OK 0 0.


Of course change device 8 to 9 in case the SD2IEC is configured at a different device address.

Edited by carlsson
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In BASIC 3.5, you can query the last disk error number and status message with the variable DS and DS$, respectively.  I am not certain if using one of the built-in DOS commands is required beforehand or not, but I suspect you will need to close the error channel before using these variables.


You should be able to power-on the device, and immediately





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I just tried the small basic prorgam and the above command and it does exactly the same as trying to




(just hangs) - When attempting to load the fB16 menu, it does say searchging for... and then just hangs like that.


I emailed the supplier and they are basically useless, first askinjg me if I'd fixed it yet and then pointing me to wards retrohax. This PCB is different to the one on that site. Similar, but different.


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I have just successfully loaded FB16 onto my Plus4 with another SD2IEC.


I know for certain my SD card is good.  Could the silk screen ATN / DATA / CLK be printed wrong, possibly?


Apart from the unit being faulty, or the firmware not being loaded to the ATmega - I'm at a loss now???

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  • 3 weeks later...

Heh, looks like someone took my layout and sells it without any info on a PCB :D

I've described this module here -> https://retrohax.net/sd2iec-revisited/


If you are getting 4.7VDC on power line then it might be a bit too small.

Also, it also hangs if you swap some of DAT/ATN/CLK wires. I do this all the time hence this suggestion ;)

Another bug, check if ALL pins on a SD slot are properly soldered. Very often, SD card detection pin is not soldered properly.

It is also possible that one of transistor is dead.


I've made around 1000 of these boards with this specific layout and I know it works with 264 series without issues.



Edited by drygol
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3 hours ago, OLD CS1 said:

@drygol I envy your collection of machines.

All of them were refurbished and found new users :)
I am not a collector but I enjoy fixing stuff :)


1 hour ago, virtvic said:

I’ll have another look at it, thanks.


it sucks that they’ve used your design and not even mentioned you on the pcb…

No problem, this is open source after all :)

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  • 9 months later...
On 9/19/2022 at 6:47 PM, virtvic said:

(just hangs) - When attempting to load the fB16 menu

did you get this sorted?

i had the same issue with 5x units i assembled. it turned out to be a bad batch of IRLML2402s that came from aliexpress.

i replaced them with ones from here in the UK and they all worked right away


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  • 1 month later...

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