SparkFun Electronics Commentsurn:uuid:214d0e4e-f1b1-d287-ce26-ac5b4c9f82492024-03-18T21:45:59-06:00SparkFun ElectronicsByron J. on Enginursday: Digging into the WerkstattByron J.urn:uuid:58a9d735-c281-b5ec-ff5e-41e774204bdf2014-10-10T15:08:03-06:00<p>OK, it seems to be helping quite a bit.<p>I'm using the first circuit from page 7 of the datasheet - 330 on series from the WS-01's 9V rail, and a trimmer across the adjust terminal. To get a suitable range from the trimmer, I had to put 10K resistors in series with the ends - otherwise it's just too darn touchy.</p><p>I'm using it a the power supply for only the one MCP4725 - the other is still hanging off 5V. I've set the ref for 5.333V. I also recalculated the LUT in the firmware, so each semitone is 64 above it's predecessor.</p><p>I've now got 49 keys of 1V/octave output, with a 0.5V range on the bender. Octaves are as in tune as I can get with the resolution of the trimpots.</p></p>
Byron J. on Enginursday: Digging into the WerkstattByron J.urn:uuid:764ed7fb-d07c-3960-8017-769e6fd2c97b2014-10-10T11:30:49-06:00<p>Will it work? I don't really know!<p>But we'll find out shortly. I just grabbed a couple of them, and a couple of trimpots...</p></p>
cmonaco on Enginursday: Digging into the Werkstattcmonacourn:uuid:64cf5302-8551-b93b-e694-4da1b0202d5e2014-10-10T07:39:45-06:00<p>I got a chance to meet the guy who designed this at Maker Faire Atlanta last weekend! Very cool to see it getting attention from Sparkfun!</p>
Customer #390482 on Enginursday: Digging into the WerkstattCustomer #390482urn:uuid:6ae95741-35a3-0e8a-28b6-fabcaf706b292014-10-09T20:45:22-06:00<p>Funnily enough, Sparkfun sells a reference volltage supply: https://www.sparkfun.com/products/11078.
Would that work, Byron?</p>
Byron J. on Enginursday: Digging into the WerkstattByron J.urn:uuid:25eb1a3e-4b57-85ff-dc80-524e2fd0bfe82014-10-09T15:59:35-06:00<p>I think it's not so much that I need a DAC with a Vref input, but that I need a source of Vref to begin with! For all I know at the moment, a 7805 or LM317 would be solid enough, and could hang from the WS's +9V rail. I don't have much experience with voltage reference supplies, and I'm not sure what the right approach is. I'm digging into a pile of datasheets and looking at other people's designs at the moment. I see the x0xB0x uses an LM336-5.0.<p>The MCP4725 seems to be OK at dividing Vcc by the right amount, so it's probably up to the task, once I get the Vref sorted out.</p><p>There are a couple of other options - I could generate a regular voltage without regard for precise scaling, and then amplify/attenuate with a trimmer to get the scaling more solid.</p><p>I've also got plenty of unused pins on the Pro-Micro. I could build a 6-bit R2R ladder, as a 1-bit-per-semitone converter. Then I could use the two MCP4725's for some combination of velocity/bend/mod/aftertouch.</p></p>
HelicopterGuy on Enginursday: Digging into the WerkstattHelicopterGuyurn:uuid:a35fb93d-29c9-c855-4720-2068f5413a2a2014-10-09T10:53:28-06:00<p>Great work! I too was thrilled to see Moog opening up to musician hackers (and possibly hack musicians).<p>The D.S. is a nice touch, too. Although I couldn't seem to find the segno when I went back.</p></p>
gskelly on Enginursday: Digging into the Werkstattgskellyurn:uuid:6389c0d3-fa7b-5d98-f616-a8732f3aa0542014-10-09T10:34:47-06:00<p>For the reference voltage issue: Microchip sells DACs with dedicated VREF pins that could be connected to a stable voltage reference. The MCP4726, for example, is pin-compatible with the 4725 except the I2C address pin is replaced with the VREF pin, so swapping out the ICs and doing some green-wire modding to the breakout board might be feasible. If you don't mind changing the firmware to use SPI instead of I2C, there's also the MCP4921 in PDIP-8 form, which would be even easier hardware-wise.</p>