A complete o_C kit!
- o_C is a fairly straightforward DAC breakout board for the teensy 3.1/3.2 ARM development board (cortex M4), with an OLED display: somewhat like a pimped-up “ardcore”, though its focus is on generating precision control voltages rather than being (entirely) general purpose (see the schematic and note re SPI below).
- To this end, the board features four 16-bit CV outputs, courtesy of DAC8565. The outputs (range: -3V/+6V) are “in-the-loop” compensated to ensure proper DC accuracy, ie. to prevent any voltage errors when connected to (the usual) 100k input impedances downstream. with suitable equipment, it’s feasible to tune the calibration points (9 per channel) accurate to +/- 0.0002V; ie tracking shouldn’t be half-bad, at all (that’s an error for pitch CVs of well under 1 cent, where a cent is one-hundredth of a standard semitone (1200 cents per octave) — the limit of human pitch difference detection is about 4 cents, thus the pitch CV tracking in O+C can be calibrated to be more accurate than your ear, or your VCOs).
- In addition, there are four CV inputs (~12 bit, -3V/+6V range, 100k input impedance) as well as four digital inputs (> 100k input impedance, threshold ~ 2.5V), two encoders (w/ switch), and two tact switches.
- As the DAC shares the SPI port with the 128×64 OLED display (teensy 3.1/3.2 only has one such port), the thing is not really suitable for applications that need to write to the DAC at audio sample rates (ie VCOs etc). that said, with some DMA trickery, and pld’s custom interleaved OLED/DAC driver (which is included in the ornament & crime firmware), the DAC update rate is 16.67kHz per channel.
More info: http://ornament-and-cri.me/hardware-basics/
- Teensy 3.1 / 3.2 dev board (Freescale MK20DX256 / 32-bit ARM Cortex M4).
- 4x precision CV outputs, 16-bit (TI DAC8565).
- output range: -3v/+6v, “in-the-loop” compensated, for proper DC accuracy (+ 9 calibration points per channel, settable in firmware); +/- 0.2mV error across a 9 octave pitch CV range is achievable.
- 4x CV inputs, -3.5v/+6.5v, 12bit, 100k input impedance.
- 4x trigger/gate inputs, threshold ~ 2.5v, > 100k input impedance.
- two rotary encoders, with built-in push switches.
- two push buttons.
- 128 x 64 pixel 1.3” OLED display (SPI / SH1106 driver chip).
- trigger-to-quantised-output latency < 100 microseconds.
- 16.67kHz internal timer (CPU overclocked to 120MHz), which is also the DAC update rate. the ADC is also read at 16.67kHz but in several of the o_C “apps”, 16 values are averaged to remove noise, meaning that the effective sample rate for CV inputs is about 1 kHz. Digital (gate/trigger) inputs are read at 16.67 KHz — this ensures very low latency.
- +/-12V power only, ca. 85mA power draw on +12V bus, < 10mA on -12V bus)