How to design a tangible programming language – Pattern Matrix at Algomech (part 2)

Once we acknowledge that weaving and programming are part of the same technological timeline, we can begin to look at the history of weaving as a eight thousand year long tale of human relationship with digital technologies – and use this long view to research new approaches to software engineering, a field with a much less developed history and many interesting problems to solve.

Using augmented reality to display dynamic information on a tangible programming language.
Using augmented reality to display dynamic information on a tangible programming language.

(Follows Part 1 here.)

One of our threads of investigation is using the pattern matrix as a general purpose tangible programming system – one that we can use for controlling swarms of robots, programming different types of weaving systems and describing complex processes, such as live musical systems.

The magnetic system on the new pattern matrix consists of four hall effect sensors on every location you can place a block. There are four unique ways you can arrange the magnets – which means four types of programming block are possible. As we want to reuse these physical blocks for various uses and programming languages, we decided to use abstract shapes to denote the block types to begin with. Each of the four blocks can be rotated and flipped to give 32 total possible orientations, or symbol ‘tokens':

All combinations of token orientation with four magnets
All combinations of token orientation with four magnets

However, only 16 of these orientations are actually unique. We can only determine flip orientation on the circular block, and only rotation on the rectangular and triangular ones – where flipping them makes no difference to the magnets. The square block is a kind of special one, as we can tell both rotation and flip orientation, so it can represent eight tokens in total all by itself:

All unique tokens and orientations possible. With mid-grey shapes the flip (which side is up) is irrelevant.
All unique tokens and orientations possible. With mid-grey shapes the flip (which side is up) is irrelevant.

It’s important to note at this point that the parallels with tablet weaving are no coincidence: rotating and flipping arrangements of four binary elements for this magnetic system are the same actions as those performed when weaving using tablets. Weaving in the pattern matrix is more than a subject, it’s built directly into it’s mode of operation.

Next we need to test the applicability of this tangible programming system for wider uses. The other cultural phenomena the Penelope project is involved in is livecoding – so is it possible to use the pattern matrix to introduce a weaving centred programming technology in a very different context, not to describe weaving but to generate music in a performance such as an Algorave? This is something that Ellen first pioneered at our weavecoding performance at The Museum of casts of classical sculptures in Munich, but the new pattern matrix has better capabilities for a general purpose programming language.

Having 16 states of four blocks is indeed limiting for a language, but not too limiting. Some types of programming language, such as a string rewriting system like a Lindenmayer system are particularly well suited to this. They are also surprisingly Turing complete languages, able to represent any other programming language in existence, given enough space and time.

Here is a quick example of how this works in text form – a string rewriting system is simply a list of search-replace actions that are carried out in a consistent order. The original example, used to model the growth pattern of algae – consists of a starting string: “A” and two replacement rules, replace “A” with “AB” and replace “B” with “A”. If we run these two rules over and over on the same bit of text we gradually ‘grow’ a pattern like this:


n = 0 : A
n = 1 : AB
n = 2 : ABA
n = 3 : ABAAB
n = 4 : ABAABABA
n = 5 : ABAABABAABAAB
n = 6 : ABAABABAABAABABAABABA
n = 7 : ABAABABAABAABABAABABAABAABABAABAAB

On the pattern matrix we use four of the rows to represent four different rules that replicate in this manner (each made of 5 possible symbols, as it’s a 5×5 grid), which we run 8 times on the starting string (A) to create a musical sequence. Four of the tokens represent these rules (A,B,C and D), the remaining tokens represent musical actions – changes in pitch, rests and sound triggers. There is massive variety of potential patterns, you can control the amount of recursion by the number of rule reference tokens you use – to control the resulting length of the sequences, and thus the complexity of the music. Interestingly we also need a ‘no operation’ (NOP) instruction that does nothing – as in low level assembler languages. We need this as a way to be able to shift timing in the musical sequence by one instruction.

A musical language in 16 instructions.
A musical language in 16 instructions.

With a tangible programming language like this it’s also very important to consider how you categorise instructions by shape – as you can quickly switch between similar operations by simply rotating or flipping tokens, while switching between different shapes takes longer (as you need to pick up a new block) so should represent bigger changes if possible.

Four rules are plenty for generating hugely complex sequences, so we can use the fifth bottom row to control global parameters like scale, synchronisation options (for our slub collaborative sync protocol) or switch between more banks of sounds for greater variety.

Slub performance including the pattern matrix at the Brighton British Science Festival Algorave
Slub performance including the pattern matrix at the Brighton British Science Festival Algorave

The first time we tried this out was at the British Science Festival Algorave in Brighton. A projection was set up with a camera to show the pattern matrix being used, and while technically everything went fine (other than some syncing difficulties), it highlighted a key problem with tangible programming languages. With no dynamic feedback other than the state of the blocks on the pattern matrix, it’s very difficult to tell what is happening during a performance, it’s hard to understand what musically is resulting from the changes you are making.

In order to find a way around this we designed an augmented reality ‘layer’ to place over the pattern matrix, which gives feedback on the currently triggered notes and the paths between the recursive string production rules. We use fluxus and it’s AR feature, which was written by Gabor Papp – which is based on the ARToolkit library. We use a printed out marker to find the plane and camera scale of the centre of the pattern matrix in the image from a USB camera. Once this is done the marker can be removed (as neither the camera or pattern matrix moves) and we can use millimetres as units and place objects over the block locations in 3D space. When the sensors detect a change we can display this new information, also updating the current position in the sequence playback to give feedback on the current sound playing.

Pattern matrix livecoding as part of slub performance at the Algomech Algorave
Pattern matrix livecoding as part of slub performance at the Algomech Algorave. Pix thanks to Dan Hett

As an initial trial the AR improved things when first tried out at the Algomech Algorave in Sheffield, it makes the pattern matrix easier to understand and perform with – and also provides some feedback for the audience in a projection. In a last minute change we switched from Latin characters to Linear A, an undeciphered ancient Greek script – a reference to Flavia’s work on the Penelope project. This is actually preferable to Latin characters as the musical language represents meaning in a way that that actual glyph used is irrelevant – it’s better if it can’t be ‘read’ or confused with another meaning by anyone (still alive).

So it seems that AR could be one of the items in our toolbox for further tangible programming experiments. Perhaps we can better explain the structural changes caused by livecoding the weaving notation for the warp weighted loom by having a dynamic weave structure ‘floating’ on top of the tokens, alongside the loom simulation. This could also be of use for describing tablet weaving actions with these blocks, which would need to be more abstract than the binary weaving notation.

Another area to explore is the design of the blocks themselves, moving away from the abstract shapes, we can design them for specific purposes. Similar to our work on viruscraft, where we have more closely explored the correspondence between physical form (receptors and structural protein arrangements) and tangible interfaces, it seems that these shapes may be worth considering more closely now the sensor matrix is working well.

Pattern Matrix at Algomech (part 1)

I’m writing this on the train with a slightly sleep deprived brain fizzing and popping from thoughts, ideas and conversations from this year’s Algomech festival in Sheffield. The Penelope project took a significant role in the festival, with the group’s participation in the Unmaking Symposium, the exhibition and also testing our latest weavecoding technology at the Algorave. I’ll be writing more on the algorave in a subsequent post.

During the symposium we discussed the critical, liberating and potentially dangerous aspects of Unmaking in a wide variety of contexts – from reverse engineering knitwear and classical Greek dance to discovering the untapped abilities of classical musical instruments when human limitations become a secondary consideration. The symposium also provided us with a good opportunity to take stock of our own group’s current directions and thinking in regard to the Penelope project.

Pix thanks to
Pix thanks to James Vanderhoven

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We also had our own corner of the Algomech exhibition, which included Jacquard woven experiments, the Quipu sonification and visualisation and the first public trials of the new pattern matrix V2.

exhib

As is our usual practice, we used this exhibition to get essential feedback on our new design for the pattern matrix, as well as the interpretation of what we are doing – being there in person talking to people allows you to very quickly determine what works, and adapt the focus based on the responses you get.

We discussed the long view on digital technology, the role of weavers in foundations of western mathematics and simply the practicalities of the technology we are developing – the constant stream of visitors represented a wide range of different ages and backgrounds. These aspects of the pattern matrix seemed significant (in no particular order):

  • The construction technique was immediately interesting to most people, specifically the material, beech wood spalting and open frame construction.
  • Related to this, there seems little association with the pattern matrix as a ‘device’ in the sense of a ‘gizmo’ – which is interesting as the Raspberry Pi and other PCBs are clearly visible. We’ve noticed this at some level with the previous version but with the wood construction this effect is much more pronounced.
  • It is seen as being game like, e.g. a “70’s educational toy”. There is an expectation that it is something to be ‘played’, and similarly its potential as a musical sequencer is a common observation.
  • The understandability of the magnet sensing seems a key ingredient. There is no other particularly hidden magic like computer vision or RFID involved, and polarity and digital arrangements of magnets are easily explained and experienced by holding the tokens together.
  • Having some extra circuit boards and wood cut parts to hand, originally intended as backups – were great for people who wanted to know more about what was going on. In future we should also have the token block parts to show as well.
  • The different shaped blocks were immediately appealing – they seemed to invite experimentation more than alternating the binary tokens by flipping them. To follow this up we need to investigate ways to use different shapes to configure thread colour at the same time as structure in a better way than we are now. The black/white sides could define structure while the shape could correspond to the colour for the specific thread. It also indicates that using shaped tokens as instructions for tablet weaving is worth experimenting with quite soon.
  • Younger children focused on the blocks alone (and of course tried all sorts of things no one else did, like stacking them) but slightly older children worked out they were having an effect on the weaving process and generally could patiently work themselves it out without any explanation required.
  • Having Anni Albers’ ‘On Weaving’ book next to pattern matrix helped with older visitors, perhaps representing a more conventional and authoritative source of information to introduce the concepts of notation, structure and pattern in weaving.
Pix thanks to James Vanderhoven
Pix thanks to James Vanderhoven
The 8-way tangible colour switching instruction
An 8-way tangible colour switching instruction

Physical vs digital – a false dichotomy

More general concepts that came up in conversation included a common theme during Algomech, exploring the inescapably fuzzy boundaries of concepts such as digital, physical and analogue. The myth of the “real world” being analogue and the “virtual world” being digital is a troublesome one to a weaver.

The ‘anti-device’ effect of the pattern matrix has the potential to explore this conundrum, as it represents a seemingly acceptable demonstration of the physical nature of the digital, and that forms of digital technology have inhabited the world of the reassuringly physical for many millennia of human invention.

Check your supply chains

One aspect of the pattern matrix I picked on for the symposium which came up in the exhibition as well was the fact that the beech wood came from a single tree in Cornwall courtesy of Aaron Moore – and used this as an example of our design philosophy of taking on the myth of collapse rather than the myth of infinite abundance.

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Feedback from Penelope team members

Having a 5X5 grid initially was thought to be excessive, as most ancient weaves can be expressed with a 4X4 matrix. This larger capability turns out to be more important than we first thought, as it means you can demonstrate the importance of odd and even numbers in the mathematics of weaving.

There is a problem with the single colour change block due to a faulty use of the code from the old version. This has always been a somewhat temporary feature so we should sort this out properly (e.g. using other shapes for colour across the matrix) before we use it next.

We can also try using an augmented reality approach to show the weave structure directly over the grid, so it’s easier to see how the token block changes relate to specific crossings. This could be displayed alongside the current warp weighted loom rather than as a replacement for it.

Pattern Matrix PCBs arrived & first tests

After triple checking the schematics and design files and ordering 80 PCBs (50 sensors and 30 i2c boards) there was an anxious wait for them to arrive and do some initial tests to find out if there were any mistakes. We now have enough boards to make two new pattern matrix devices, one 4X4 and one 5X5 – the plan is to evaluate the design and refine it for future builds.

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The picture below shows the first test boards populated and plugged it into the Pi – it’s much neater than the lego and breadboard prototype! The good news is that it seems to work so far, the only problem I’ve had is with the hall effect sensors, the pads are a tiny bit too close together for my skills. After a couple of tricky situations fixed with a de-soldering pump, I think I’ve come up with a strategy that works. I can bend the outer pins away from each other and solder the central pin first – then bend them back to finish the outer ones and being very careful not to bridge the pads.

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The blue jumpers on the square i2c boards allow you to program the device channel that the two expanders use – these could alternatively be hard soldered, but it’s good to have the option to reuse the parts or reconfigure a pattern matrix so we can add different sensors etc.

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For reference, the KiCad 3D viewer models look pretty close.

i2c-render

sensor-render

PCB design for pattern matrix 2

This is the pattern matrix 2 tangible sensor schematic, which is fairly simple – just 4 hall effect sensors and a capacitor to smooth out any noise on the power supply.

sensor-schematic

We need to make hundreds of these for the Penelope Project, and we can save some costs by using the built in pull up resistors in the MCP32017 to get a decent signal from the sensors. The difficulty with this PCB is arranging the sensors so they align with the magnets in the tangible programming block in the optimum manner. From tests with the prototype Lego rig, this isn’t actually too critical – but it’s set up so the lead length can be tweaked a bit at soldering time.

sensor-render

This took me about 20 variations to finally get right, but the circuit is just about simple enough that it can be made single sided – this is good because the top side will be partly exposed, while the lower side with all the copper traces can be protected. It’s good practice to have large areas of copper left connected to ground, partly as it’s a common connection needed all over the board, partly for stability but also it reduces the amount of chemicals required to etch the circuit – as only the parts around the traces need to be removed.

sensor-render2

The i2c expander board is a little more complicated. The design is made to be modular so we can stack up any number of these connected to the Raspberry Pi for different arrangements of sensors. Each board can deal with 8 sensor locations (each comprising 4 individual hall effect sensors). Their job is to convert the digital signals from each sensor into serial data (using the i2c protocol) so the Raspberry Pi can read them all just using 2 wires, plus 2 for power.

i2c-schematic

Each board can be configured to a separate i2c device address to tell it apart from the others using jumper connectors. This one had to be 2 sided, but I managed it without any ‘vias’ (holes to pass traces from one side of the board to another). I also added a power indicator LED as a last minute addition.

i2c

I’ve been learning the open source Kicad software to design these, which is now used by CERN for building the LHC, so it’s pretty fully featured! The idea is that you draw the schematic first, link each component with a physical ‘footprint’, then switch to the PCB design stage. Other software I’ve used in the past tries to route everything in one go for you (and can come up with some pretty strange and messy results). Kicad works in a semi-automatic manner – you need to draw each trace by hand, but it routes them around components and other traces, and suggests the shortest path for you. This is quite a lot better than a fully automatic approach as you have more control over the end result, and easily end up with a decent placement of all the parts.

i2c-render

This project is of course open hardware, and can be found on github here.