Grandbot is a robot grand-child for my parents. He's my my take on Mohit Bhoite's Chintoo.
- Grandbot is a generative, pattern-based MIDI arpeggiator
- He has different moods based on his self-esteem. These moods affect everything from his expressions, the color of his light, and the sounds he plays.
- To increase his self-esteem, it's important to give him plenty of attention. He currently can be interacted with using a "play" button; if you play with him, he feels better about himself and he gets happier.
- He doesn't like to be ignored though. If you don't play with him regularly, he starts to feel unimportant. If his self-esteem drops too low, he gets depressed.
- He uses a photoresistor to determine when to go to sleep and when to wake up.
- He has an onboard passive buzzer and uses it to make music. The music is mostly randomly generated and is influenced by his mood.
- He likes to set mood lighting using an RGB LED as another indicator of how he's feeling.
I had extra memory, so I decided to program Grandbot to play synths with me. He's now a chaotic, generative, pattern-based arpeggiator.
This requires the additional MIDI board for Grandbot.
The simplest use:
- Plug something that can send MIDI notes and a MIDI clock to Grandbot's MIDI input
- Plus Grandbot's MIDI out into a synth
- Start the MIDI clock and play some notes
- Press the button to generate a new sequence
There's endless potential just doing that. If you'd like more control, there are additional parameters that can be changed using MIDI CC:
| Description | MIDI CC | Display | Button |
|---|---|---|---|
| » Sequence Parameters | |||
| Base note length | 20 | nL | |
| Sequence length | 21 | SL | |
| » Transposition Chance | |||
| One octave up chance | 22 | o- | |
| One octave down chance | 23 | o- | |
| Two octaves up chance | 24 | o= | |
| Two octaves down chance | 25 | o= | |
| Fifth up chance | 85 | Ft | |
| Random transposition chance | 86 | rn | |
| Rest chance | 29 | rE | |
| » Note Length Chance | |||
| Double length chance | 26 | dL | |
| Half length chance | 27 | HL | |
| Ratchet (double note) chance | 28 | rA | |
| Random length chance | 87 | rL | |
| Note run chance | 30 | ru | |
| » Generate / Slip | |||
| Queue sequence generation | 118 | * | |
| Slip chance | 89 | SC | |
| Queue sequence slip | 116 | * | |
| » Utilities | |||
| Swing (50-67%) | 115 | SG | |
| Note sort | 114 | So | |
| Select MIDI channel in | 14 | In | |
| Select MIDI channel out | 15 | ot | |
| Panic / all notes off | 117 | AH | * |
| Toggle internal speaker for arp | 119 | SP |
Additional Notes
- Things marked as buttons have to go low (CC 0) before going high (CC 127) to trigger
- Defaults
- MIDI in: listen to all channels
- MIDI out: send on channel 1
- Base note length: random
- Base sequence length: random
- Speaker: off
- Chances have sensible defaults depending on what they do
- Generate / Slip
- Generate uses chance to generate a new sequence
- Generate triggers at the end of the bar
- Slip randomly swaps notes in a sequence based on slip chance
- Slip triggers at the end of the sequence
Tip
Changing variation chances only affects new sequences, not the current sequence. Press the button after making changes to hear the effects.
Warning
Pretty much all of these are only affected if the commands happen on the selected MIDI in channel (by default Grandbot listens to all channels). However CC 14 (MIDI in selector) and CC 117 (Panic) listen for changes on all channels all the time.
Grandbot development is what I'm using to learn more about electronics and C++. I write about what I've been learning on my blog. Here are the Grandbot posts:
- Grandbot: Sleep
- Grandbot: Voice
- Grandbot: Play
- Grandbot: Light
- Grandbot: MIDI & Misc
- Grandbot: Arp
- Concurrent Arduino
- 4 Digit, 7 Segment Emoji
- Max7219 Emoji
One digit of an expression looks like B00000000. For the first four digits, it maps to:
- B: specifying it's binary
- 0: the decimal point (DP)
- 0: top horizontal line
- 0: top right vertical line
- 0: bottom right vertical line
- 0: bottom horizontal line
- 0: bottom left vertical line
- 0: top left vertical line
- 0: center line
The fifth digit:
- B: specifying it's binary
- 0: the center colon
- the reset are unused
The sixth digit:
- B: specifying it's binary
- 0: the top dot
- the reset are unused
This was originally built on a cheap Arduino Nano clone.
However I wanted to be able to support 8 bars of 32nd notes in the arpeggiator (the minimum base note length is 16th, but ratchets break that into 32nds) and the Arduino Nano didn't have enough memory. The Arduino Nano Every does! It's a different board with a similar name.