Rockit Software Version 1.1 and Hardware Hacks

I’ve been hard at work on Rockit’s firmware and am proud to put out Version 1.1. There are a number of improvements, bug fixes, and a new feature. I’ve also made a few adjustments/hacks to resistor values which greatly improve Rockit’s sound. Click through for a list of the software and hardware updates.Filter Envelope – There were many requests to improve Rockit’s filter envelope speed and I’m very happy with the changes. I greatly increased the speed of the envelope processing. The new envelope can be so fast it creates these crazy laser sounds. Sci-fi effects artists are officially on notice. I also maintained the long envelope times for making sweeping pad sounds for all you experimental types. In general, the filter is faster, including it’s response to the LFO. I really like the sound of the LFO modulating the filter at high frequency. The envelope also now loops when in Drone Mode. This really brings Drone Mode to life.

Pseudo 9-bit Filter – I modified the software side of the analog filter so that it would take advantage of the fact that each filter uses two 8 bit digital potentiometers. Two times 8 bits gives you 9 bits. I used this to reduce the filter artifacts at the high end of the cutoff frequency and to linearize the filter pot control and filter resonance control.

Here’s a sample playing with the new filter:

Pitch Bend – It’s now one octave up and one octave down. There was also a problem with the pitch bend not shutting completely off when used. Consider it fixed.

Oscillator Off – If the oscillator knob is turned all the way to the right, the oscillator will be off. This makes it so the filter and it’s envelopes can be used without any oscillator running.

Detune – Related to the pitch bend, I fixed a bug which would cause the detune function not to work. This was especially a problem in Drone Mode. Fixed that.

MIDI – I created a method to remember which keys were played. This allows keys to be held and released, played again, and back and forth. This allows for creating alternating held notes. It’s also critical for the new feature.

New Feature – I created an arpeggiator. This is particularly useful for Drone Mode, which is where it is most easily accessed. In Drone Mode, the arpeggiator pattern is selected by turning the ADSR Decay knob. The speed of the loop is determined by the ADSR Release knob. The pattern that is selected remains when Rockit leaves Drone mode, so that there is a hardware way to select the arpeggio and the playback rate. The simplest pattern is when the arpeggiator is on pattern 1, which plays back the sequence of held notes in the order they were pressed. The other patterns are transpositions of notes in a sequence. I think this makes for a method of making very interesting arpeggiations.

Here’s some playing with the arpeggiator in Drone Mode:

I’ve put this new software as a .hex file on the Rockit Source Code Page.

I’ve also made some changes to the hardware. These are just resistor changes, so they are easy for anyone to make. All new kits and synths will ship with these changes.

R7 and R34 – They were 470 Ohms. The new value is 100 Ohms. This change greatly improves the high frequency of Rockit’s sound. It’s a pretty huge change and is highly recommended.

R16 – It was 100 Ohms. The new value is 220 Ohms. This increases the overall volume of Rockit and improves the Signal to Noise ratio. This change is dramatic.

R17 and R18 – The old value was 1.5k. The new value is 1k. This increases the maximum frequency of the low pass filter. It allows for maximum open filter sound with nice high frequencies. You can go lower than 1k to get an even higher low pass maximum cutoff frequency. I leave it with you to play with, but I’ve found that 1k is a happy value.

All kits since last week have been shipping with these new values and all future kits will too. I will be modifying the Bill of Materials and Assembly Instructions accordingly.

With all of these changes together, I think that I’ve addressed all the comments that I’ve received and added a bit of extra goodness. I hope you enjoy the changes!

P.S. Sprockit will be benefiting from all of these changes and by the way, I’m almost finished with Sprockit’s hardware design!




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      • You shouldn’t have to do anything with the fuses unless you’re programming a micro from scratch. If you do need to though, the fuses that should be on are: SPIEN, WDTON, and EXTERNAL OSCILLATOR 8MHZ+,16Clk,65ms. CKDIV8 and JTAGEN should be off.

  1. Great!

    I also tried building and uploading the code, but the source on Sourceforge is still v1.01. Could you post v1.1 of the source?


    • You’ll need header pins and a programmer too. I’m thinking about putting a MIDI bootloader on, but that won’t help you because you’ll need to program it with the AVR ISP connection to put it on there.

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