Open Source/Freeware Budget USB DAC

[mixedgas]

That would sadly make the board much more expensive and complicated. The problem is not USB's bandwidth, it is the bandwidth of the USB chipset we are using.

If the ethernet rabbit board is truely 35$???

Steve

[heroic]

If the ethernet rabbit board is truely 35$???

Steve

Given that we're trying to keep this thing under $100 in parts, and the Rabbit board is not even close to being fast enough (believe me, I've used them), another $35 for a Wiznet chip, magnetics and connector is out of the question; never mind the fact that these things connect via SPI, which means we don't have enough bandwidth.

[mixedgas]

Given that we're trying to keep this thing under $100 in parts, and the Rabbit board is not even close to being fast enough (believe me, I've used them), another $35 for a Wiznet chip, magnetics and connector is out of the question; never mind the fact that these things connect via SPI, which means we don't have enough bandwidth.

Which would serve us better FTDI or PIC 18F2455 USB engine? DR L does pic. I do board layout in eagle and PCBARTIST

Steve

[heroic]

Which would serve us better FTDI or PIC 18F2455 USB engine? DR L does pic. I do board layout in eagle and PCBARTIST

Steve

Well, the EasyLase uses the FTDI, so clearly it's workable :-)

How about instead of an ATmega we use one of the ATxmega parts? They have onboard DACs.

http://atmel.com/dyn/products/produc...N=ATxmega256A1

[mixedgas]

ardunio with shield is looking best at this point.

Steve

[drlava]

How about instead of an ATmega we use one of the ATxmega parts? They have onboard DACs.

http://atmel.com/dyn/products/produc...N=ATxmega256A1

I like that solution. Powerful MCU, fast 12 bit DAC pair built in, plus you get your 8-channel A/D sampling, pair it with one or two TLV5627 quad 8-bit DACs running at 20MHz SPI or TLC7225 for parallel signaling and that's a nice, inexpensive bit of kit with enough headroom for some more advanced safety or linearization functions.

[heroic]

I like that solution. Powerful MCU, fast 12 bit DAC pair built in, plus you get your 8-channel A/D sampling, pair it with one or two TLV5627 quad 8-bit DACs running at 20MHz SPI or TLC7225 for parallel signaling and that's a nice, inexpensive bit of kit with enough headroom for some more advanced safety or linearization functions.

Can we please use 12-bit DACs all round? I need more than eight bits.

Actually, this part has four 12-bit DACs on die:

http://search.digikey.com/scripts/Dk...MEGA64A1-AU-ND

It also has the awesome advantage of being (a) in stock and (b) in a package I can hand solder.

[drlava]

Can we please use 12-bit DACs all round? I need more than eight bits.

Actually, this part has four 12-bit DACs on die:

http://search.digikey.com/scripts/Dk...MEGA64A1-AU-ND

It also has the awesome advantage of being (a) in stock and (b) in a package I can hand solder.

Looks like it has 2 DACs each with 2 sample and hold outputs. How about pairing that with a DAC124S085. The SPI of this chip would work to the full 32MHz of the AVR. But it's the same cost as another AVR. Hmmm

[heroic]

Looks like it has 2 DACs each with 2 sample and hold outputs. How about pairing that with a DAC124S085. The SPI of this chip would work to the full 32MHz of the AVR. But it's the same cost as another AVR. Hmmm

I actually really prefer the Microchip DACs because they're available in DIP, which means we can place a socket and let people who need more than four analogue channels (ie., people with more than two lasers) fit it at will. That makes it cheaper at the entry level.

[drlava]

but with the DACs on the atmel the total is 6 or 8 12 bit analog outputs. The single, quad external DAC chip is not expensive enough to warrant socketing four single DIP DACs, IMO. Plus the single quad will take up less board real-estate.