[Coco] Cheap alternative to the DE-1?

Wed Oct 28 16:36:33 EDT 2015

I think the R2R network would yield more precise voltages although you'd 
need more resistors.  The DE1 board uses a simple binary-weighted DAC 
and it seems to function fine. If you were doing 'photoshop' work then I 
suppose you would find the extra accuracy necessary but apparently the 
simple DAC works pretty well.

Dave

On 2015-10-28 15:20, CoCo Demus wrote:
> Wouldn't a R2R network more efficient ? As it keeps the R impedance ? 
> On
> RGB2VGA I use it.
> 
> On Wed, Oct 28, 2015 at 1:15 PM, Dave Philipsen <dave at davebiz.com> 
> wrote:
> 
>> Actually, three resistors per channel would yield 512 colors 
>> (including
>> black). Three bits yields 8 combinations or voltage levels or colors 
>> per
>> channel.  There are 3 colors (RGB) or channels so 8 to the third power 
>> is
>> 512.
>> 
>> If you bump it up to four bits per channel you can have 4096 colors.
>> 
>> Dave
>> 
>> 
>> 
>> On 2015-10-28 13:40, Zippster wrote:
>> 
>>> Probably a binary weighted DAC (resistor network) like many dev 
>>> boards.
>>> Three resistors per channel should give 64 colors (4 levels including
>>> ground level per channel).
>>> Add another bit per channel to go to 125.
>>> 
>>> USB blaster clones are dirt cheap on eBay.  Like $4 or so.
>>> 
>>> - Ed
>>> 
>>> 
>>> On Oct 28, 2015, at 12:51 PM, Dave Philipsen <dave at davebiz.com> 
>>> wrote:
>>>> 
>>>> Well, the DE-1 doesn't have a DAC either, just a resistor network.  
>>>> You
>>>> could probably hack that board though to get more colors if you 
>>>> wanted.
>>>> 
>>>> Another thing you'd have to consider on this board is that it 
>>>> doesn't
>>>> have the built in USB Blaster like the DE1.  You'd have to buy a 
>>>> blaster on
>>>> eBay or somewhere.  If you are patient you can sometimes find a DE1 
>>>> on eBay
>>>> that will go for around $90 or so.  I even saw one go for around $55 
>>>> bucks
>>>> once.  My experience finds that they are usually in excellent 
>>>> condition.
>>>> 
>>>> Dave
>>>> 
>>>> 
>>>> On 2015-10-28 12:32, tim franklinlabs.com wrote:
>>>> 
>>>>> Yeah, you're probably right. I found another problem too. I found 
>>>>> the
>>>>>   schematic for it and they limit the video to 8 colors. Not DAC to 
>>>>> the
>>>>>   VGA connector. Just logic.
>>>>>   Manual: [1]http://www.dukelanovic.com/A-C8V4%20MANUAL.pdf
>>>>>   Schematic:
>>>>>   [2]
>>>>> http://d1.amobbs.com/bbs_upload782111/files_44/ourdev_671042EUF7C8.p
>>>>>   df
>>>>>   Shorter links too LOL!
>>>>>     On October 28, 2015 at 12:23 PM Dave Philipsen 
>>>>> <dave at davebiz.com>
>>>>>     wrote:
>>>>>     FWIW, I think Gary's project uses north of 9,000 LEs which 
>>>>> means
>>>>>     that
>>>>>     even if you can trim it down to fit you won't have a lot of 
>>>>> extra
>>>>>     space
>>>>>     for future expansion/additions. Not trying to be negative...I 
>>>>> hope
>>>>>     you
>>>>>     get it working...would be an interesting project.
>>>>>     Dave Philipsen
>>>>>     On 2015-10-28 07:23, tim franklinlabs.com wrote:
>>>>>     > I ran across this while surfing E-Pray this morning. It looks
>>>>>     > interesting. For those, like me, who are interested in 
>>>>> FPGA's,
>>>>>     this
>>>>>     > $70.00 unit seems to have everything needed to port Gary 
>>>>> Beckers
>>>>>     > CoCoFPGA to it:
>>>>>     >
>>>>>     >
>>>>>     >
>>>>>     [1]
>>>>> http://www.ebay.com/itm/Altera-Cyclone-NIOS-II-SOPC-FPGA-Developm
>>>>>     ent
>>>>>     >
>>>>>     >
>>>>>     
>>>>> -Learning-Board-EP2C8Q208C8N-LCD1602/272020523309?_trksid=p2054897.c
>>>>>     100
>>>>>     >
>>>>>     >
>>>>>     
>>>>> 204.m3164&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D2
>>>>>     014
>>>>>     >
>>>>>     >
>>>>>     
>>>>> 0407115239%26meid%3D8d211755ec994eff8913982e805be0c8%26pid%3D100204%
>>>>>     26r
>>>>>     > k%3D12%26rkt%3D21%26sd%3D261661704545
>>>>>     >
>>>>>     > It uses a smaller FPGA so there may be a limit here. I'm not 
>>>>> sure
>>>>>     > how
>>>>>     > many LE's Gary's code uses.
>>>>>     >
>>>>>     > This board: EP2C8 8,256 LE's
>>>>>     > DE-1: EP2C20 18,752 LE's
>>>>>     >
>>>>>     > Also, there are only 2 PLL's and I'm not sure if both are
>>>>>     connected
>>>>>     > to
>>>>>     > clocks. I bought a small FPGA that had 4 clock inputs with 2
>>>>>     PLL's.
>>>>>     > The
>>>>>     > moron who designed the board connected the clock to one of 
>>>>> the CLK
>>>>>     > pins
>>>>>     > not connected to the PLL's.
>>>>>     >
>>>>>     > This board: 2 PLL's This assumes there are clocks connected 
>>>>> to
>>>>>     > both.
>>>>>     > DE-1: 4 PLL's DE-1 uses only 3 (one connected to the
>>>>>     > external clock)
>>>>>     >
>>>>>     > Since Gary posted an "almost" up to date project of his 3.0 
>>>>> FPGA
>>>>>     > code,
>>>>>     > i went ahead and bought one to see if I can port it. It comes 
>>>>> from
>>>>>     > China, so it wont arrive for a while (slow boat from china 
>>>>> joke in
>>>>>     > real
>>>>>     > life). I'll keep everyone posted.
>>>>>     >
>>>>>     > References
>>>>>     >
>>>>>     > 1.
>>>>>     >
>>>>> 
>>>>> http://www.ebay.com/itm/Altera-Cyclone-NIOS-II-SOPC-FPGA-Development
>>>>>     
>>>>> -Learning-Board-EP2C8Q208C8N-LCD1602/272020523309?_trksid=p2054897.c
>>>>>     
>>>>> 100204.m3164&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%
>>>>>     
>>>>> 3D20140407115239%26meid%3D8d211755ec994eff8913982e805be0c8%26pid%3D1
>>>>>     00204%26rk%3D12%26rkt%3D21%26sd%3D261661704545
>>>>>     --
>>>>>     Coco mailing list
>>>>>     Coco at maltedmedia.com
>>>>>     https://pairlist5.pair.net/mailman/listinfo/coco
>>>>> References
>>>>>   1. http://www.dukelanovic.com/A-C8V4%20MANUAL.pdf
>>>>>   2.
>>>>> http://d1.amobbs.com/bbs_upload782111/files_44/ourdev_671042EUF7C8.pdf
>>>>> 
>>>> 
>> --
>> Coco mailing list
>> Coco at maltedmedia.com
>> https://pairlist5.pair.net/mailman/listinfo/coco
>> 