Open Source/Freeware Budget USB DAC

[heroic]

If we don't use the serial port we can throw in DMX too...

If we don't use the serial port, we can use the Arduino software and libraries, and make it super easy for people to hack on the firmware. This is good.

[keeperx]

as hopeful and excited as i am about new projects, i have seen this perticillar project picked up and dropped 3 time in my short laser experience.. this thread has been open since 2007... is this actually gonna happen?? that may sound negative, and i am normally the bandwagon guy who gets behind every new idea, but this one has let me down before...

[drlava]

was that an offer to get down and dirty, learn and help out?
If not, just wait and see.

[mixedgas]

it helps to have inputs, analog or otherwise.

would be nice to get at the 2nd timer for beat sensing.

there are alternate architectures, the pics with USB, the atmels with USB engines, and v-usb, one cheap processor doing the v-usb and one doing the output.

Steve

[cfavreau]

Ok now we shoot the engineer. This is supposed to be a budget DAC. The bare minimum to keep it a useful engine for a while. We start adding stuff now and it will never get done.

KeeperX -> Yeah it might end up that way. Hoepfully laying down a nice set of solid specs and getting too carried away will help it along.

Heroic -> I would definitely like to use the Arduino libraries. In fact a new Ardunio just stepped out. The Arduino Mega:

http://arduino.cc/en/Main/ArduinoBoardMega

We could use that as a base design ... and like the Boarduino's keep the serial port TTL unless you plug in a TTL to serial adapter for programming. Then we can keep it cheap. No sense on using 2 USB to serial converters (USB->Serial) + (USB->Parallel). Unless we can figure out a way to squish the bandwidth we need into 2 Mbps to 3 Mbps ... then we can use the FT232R and we can use a Arduino Mega and just make a Shield (add on board for it). That would be ideal. 60kpps with all the extra stuff would be hard to do though.

So are we done with the specs?
~$100
USB Interface
60 kpps max output rate (1 to 60 kpps variable)
12 bit X/Y
8 bit RGB(V to be determined)
8 bit TTL (including shutter)
Open Source
Easy to use tools
Good Documentation on Micro + Chips
Open DLL API

If so... then let the engineering begin. If anyone has an existing design that will fit ... please post here I guess (even if it is posted somewhere else).

[heroic]

Ok now we shoot the engineer. This is supposed to be a budget DAC. The bare minimum to keep it a useful engine for a while. We start adding stuff now and it will never get done.

KeeperX -> Yeah it might end up that way. Hoepfully laying down a nice set of solid specs and getting too carried away will help it along.

Heroic -> I would definitely like to use the Arduino libraries. In fact a new Ardunio just stepped out. The Arduino Mega:

http://arduino.cc/en/Main/ArduinoBoardMega

We could use that as a base design ... and like the Boarduino's keep the serial port TTL unless you plug in a TTL to serial adapter for programming. Then we can keep it cheap. No sense on using 2 USB to serial converters (USB->Serial) + (USB->Parallel). Unless we can figure out a way to squish the bandwidth we need into 2 Mbps to 3 Mbps ... then we can use the FT232R and we can use a Arduino Mega and just make a Shield (add on board for it). That would be ideal. 60kpps with all the extra stuff would be hard to do though.

So are we done with the specs?
~$100
USB Interface
60 kpps max output rate (1 to 60 kpps variable)
12 bit X/Y
8 bit RGB(V to be determined)
8 bit TTL (including shutter)
Open Source
Easy to use tools
Good Documentation on Micro + Chips
Open DLL API

If so... then let the engineering begin. If anyone has an existing design that will fit ... please post here I guess (even if it is posted somewhere else).

I want six 12-bit DACs. I don't care if we only actually use 8 bits of the colour ones, or use 16 bit DACs, or whatever, but I want six DACs that are at least 12 bits. Don't let the wire protocol dictate the hardware.

I already posted my design for this (and seriously, the MCP4921 DACs are small, cheap, available in through-hole, and if we use the single DAC chips then the cheapskates need only populate as many channels as they want to use.)

I'd also like access to six of the analogue inputs on the micro (you'll see why later...) and a piggyback connector for a second "shield" board...

-J.

[mixedgas]

I want six 12-bit DACs. I don't care if we only actually use 8 bits of the colour ones, or use 16 bit DACs, or whatever, but I want six DACs that are at least 12 bits. Don't let the wire protocol dictate the hardware.

I already posted my design for this (and seriously, the MCP4921 DACs are small, cheap, available in through-hole, and if we use the single DAC chips then the cheapskates need only populate as many channels as they want to use.)

I'd also like access to six of the analogue inputs on the micro (you'll see why later...) and a piggyback connector for a second "shield" board...

-J.

I think you want to trust her on this one.....

Steve

[keeperx]

I want the final product to be able to handle the shutter loop and the big red button.

[cfavreau]

It takes 1.6 us to write to 1 DAC appx (not including the SS pin and misc. overhead - 16 bits per xfer). that is ideal and at 10 MHz SPI clock rate (the max the ATMega family can do). You have to do this x 6 = 9.6 us ... so you now have ~7 us left to transfer data and do other house keeping. Seems doable.

The only other thing would be how to transfer all of the data from the PC to the micro. That is a nice chunk of data. What are the plans?

[mixedgas]

I want the final product to be able to handle the shutter loop and the big red button.

Already taken care of 6 posts ago.

Shutter will be TTL output along with 7 other IO lines. users can then interface as needed. The CPU does not need to see the BRB/Keyswitch per CDRH, it only has to break the loop, so that is also a user wiring thing. we may put pads or a transistor on the board for it, but the TTl can drive a user provided opto 22 relay , and we dont want shutter EMF spikes coming into our controller.

Steve