TinkrkniT

What is TinkrkniT?

TinkrkniT lets you design colorwork on your computer and knit it on your knitting machine, without punch cards or the machine's own console. You still knit by hand, pushing the carriage across the bed as usual. TinkrkniT chooses the needles for every row and tells you when to change yarn.

It's made of two parts that work together:

• TinkrkniT, the design software. It runs in your web browser. You draw your design in it, check that it can be knitted, and then knit from it.
• TinkrkniT Controller, the hardware. It's a small box that sits between your computer and the knitting carriage, with a screen, a button and two lights. It tells the carriage which needles to select.

The design tools aren't tied to any particular machine. Knitting from the app works with Silver Reed and Knitmaster electronic machines, using TinkrkniT Controller. See Compatible machines.

While you knit, your design is sent to the controller one row at a time. Each pass of the carriage knits one row, and the next row is sent as soon as the pass is finished. When the next pass needs a different yarn or carriage setting, both the app and the controller tell you before you start it.

In this guide, the app means TinkrkniT and the controller means TinkrkniT Controller.

What you'll need

Compatible machines

To knit from the app, TinkrkniT Controller needs a machine with an electronic patterning carriage. These machines should work, but only the SK840 has been tested so far. Try the others at your own risk (see Before you start).

Designing works for any machine, or none. The design tools aren't tied to a machine, so you can use TinkrkniT to chart colorwork for a punch-card machine, another make of electronic machine, or hand knitting. Print the chart or a knitting plan from Exporting files.

Getting the software

TinkrkniT runs in your web browser. There are three ways to run it, all the same app, and any of them can also be installed as an app.

To knit from TinkrkniT, use Chrome or Edge (or Firefox 151 or newer). These are the browsers that can talk to a USB device, which the knit screen needs. Any browser can be used for designing; the Knit button shows a dot where knitting isn't available.

Use it online

Open tinkrknit.com/app. That's all you need to design.

Your designs are saved in your browser, not on our server. To keep a copy somewhere else, use the backup rows in the File menu:

• Back up library downloads one file with every project, stamp and yarn.
• Back up to a folder (Chrome and Edge) keeps a backup up to date in a folder you choose. Choose one inside OneDrive, Dropbox or iCloud and the copy is off your computer too.
• Restore from backup adds what's in a backup file to your library.

The online app updates itself the next time it opens with a connection.

Installing it as an app

Installing gives TinkrkniT its own window and a desktop or Start menu shortcut, and lets it open without an internet connection.

• Chrome or Edge: click the install icon at the right of the address bar, or choose File › Install TinkrkniT.
• Safari on a Mac (macOS 14 or later): File › Add to Dock.

Once it's installed in Chrome or Edge, double-clicking a .knitproj file opens it in TinkrkniT.

Run it with Docker

Host it on a PHP server

You'll need PHP 8.1 or newer, and pdo_sqlite if you want server storage.

1. Download the release zip, or git clone the repository.
2. Point the web server's document root at public/. src/, schema.sql and data/ stay beside it, outside the web root.
3. Choose where designs are saved: copy config.example.php to config.php and set storage:
   • 'browser' (the default): each visitor's designs stay in their own browser. Use this for anything public.
   • 'server': one library in data/knit.sqlite, shared by everyone who can reach the server. Make data/ writable by the web server.

To try it on your own computer, run php -S 127.0.0.1:8080 -t public and open http://127.0.0.1:8080. To update, replace the files; config.php and data/ are left alone.

Opening it from another computer

Knitting and installing as an app both need the page to come from https://, localhost or 127.0.0.1. A copy opened by its network address, such as http://192.168.1.20:8080, still lets you design but can't knit or be installed. To use it from another computer, put it behind HTTPS, or open it on the computer plugged into the machine.

Getting the controller

You don't need to know how the controller is built to use it. If you'd like to build your own, or repair or modify one, see Controller Hardware.

Source code and files

How this guide is organised

New to TinkrkniT? Read Setting up the controller, then follow Your first piece.

A tour of the designer

This is what you see when you open the app. The big grid in the middle is your repeat tile: one copy of the motif, one square per stitch. The darker copies around it are "ghost repeats" showing how it continues across the panel.

1. ToolbarFile, Project, Library, Calculators and Export on the left; Save and Knit in the middle; Preview and View on the right. The project's name sits beside the logo and you can click it to rename the project.
2. ToolsThe drawing tools. See Drawing tools.
3. ColorsYour palette, and which color each mouse button paints. See Colors and yarns.
4. StitchesThe knitting technique, and which layer you're drawing on. See Techniques.
5. Options barSettings for the tool you're holding, such as brush size or mirror drawing. See The options bar.
6. The gridYour repeat tile. Row numbers run up the left side from the cast-on edge, and stitch numbers run along the top.
7. View controlsUndo and redo, zoom in and out, and Fit to fit the tile in the window.
8. Panel previewThe whole panel as knitted fabric. See Previewing the fabric.
9. KnittabilityWhether the machine can knit what you've drawn. See Knittability.
10. Status barThe tile and panel size (click to change them), the knittability badge, and the stitch and row under the mouse.

Tile and panel

Two sizes matter in every project:

• The panel is the whole piece of knitting, for example 120 stitches by 160 rows for a hat.
• The repeat tile is the motif you draw, for example 24 × 24. The app repeats it across and up to fill the panel.

The status bar always shows both, for example Tile 24 x 24 · Panel 120 x 160. Click it to change them in Project settings.

Moving around the grid

• Zoom with the mouse wheel or the − and + buttons. Fit (or 0) fits the tile to the window.
• Pan by holding Space and dragging.
• Undo and redo with the arrow buttons, Ctrl+Z and Ctrl+Shift+Z (or Ctrl+Y).

Drawing tools

Click a tool, or press its letter on the keyboard. Hover over a tool to see a reminder of what it does.

Most tools paint with the drawing color on the left mouse button and the base color on the right. You choose both in the Colors panel.

The options bar

The strip above the grid holds the settings for whichever tool you're using. It changes as you switch tools. You can hide it from the View menu if you want more room.

Selections, copy and paste

With the Select tool (M), drag a box over the grid. The options bar then shows everything you can do with it:

Press Esc to drop the selection. The copy only lasts while the app is open: it isn't shared with other programs.

Colors and yarns

Each project has its own palette of numbered slots. The design stores slot numbers, not colors, so changing a slot's color repaints every stitch that uses it.

• Click a swatch to make it the drawing color (marked D, left mouse button).
• Right-click a swatch to make it the base color (marked B, right mouse button).
• The arrows between them swap the two.
• Number keys 1–9 pick a slot.

Underneath, you can edit the selected slot: its Color, its Name, and which Yarn from your stock it stands for. Linking a yarn uses that yarn's color and name, and lets the yarn estimate work out how much of it you need. Add slot and Remove change the palette size (it always keeps at least two slots).

Slot 1 is the background: the eraser paints with it, and a new tile is filled with it.

Techniques

The Stitches panel sets how the design will be knitted. The same drawing can be knitted several ways, so the technique is a setting, not part of the drawing. It's also on the Details tab of Project settings and at the top of the Knittability panel.

Stitch chart from colors

Slip stitch and Mosaic offer Stitch chart from colors. It writes out the passes the machine will make as an editable tuck & slip chart, one chart row per pass, so you can fine-tune individual passes. Back to colors brings back your original drawing.

With these techniques one drawn row takes several passes, so the rulers, status bar and knit screen count drawn rows and show the pass beside them, for example row 40, pass 3 of 4.

The stitch layer

Besides colors, a project has a second grid of stitches: knit, tuck or slip. Layer in the Stitches panel (or Q) switches which one you draw on. Every tool works on either layer. On the stitch layer, the number keys pick knit, tuck or slip, and the right mouse button paints knit.

The stitch layer is only knitted with the Tuck & slip technique. If you draw on it with another technique, the panel says Not knitted and offers a link to switch to Tuck & slip.

A single row can tuck or slip, but not both: the carriage is set for one or the other on each pass.

Stamps

A stamp is a saved motif you can place again and again, in any project. The Stamps panel (closed when you first open the app; click its title to open it) shows your recent stamps. Click one to pick it up, then click the grid to place it.

All stamps opens the full list in the Library. Save selection as stamp saves whatever you've selected.

While you're holding a stamp, R turns it a quarter turn (Shift+R turns it back), and the arrow keys nudge the one you just placed. Stamps remember their colors, so when you drop one into a project with a different palette, each color is matched to the nearest slot.

Previewing the fabric

The Panel preview shows the whole panel with the repeats filled in. Choose how it's drawn from the list under it:

• Scroll to zoom and drag to move around. −, + and the percentage in the corner zoom too (the percentage fits it again).
• Repeat marks outlines each copy of the tile.
• Full window (or P, or the toolbar's Preview button, or a click on the preview) fills the window with it. Press Esc or Close to come back.

Knittability

The Knittability panel checks your design against the rules of the technique you've chosen, as you draw. It never stops you drawing: it just tells you what won't work.

• Judged as shows the technique. Click it to change technique.
• Floats are the strands of unused yarn carried across the back in Fair Isle. Long ones snag. Flag floats longer than sets the limit (7 stitches to start with). Break up long runs with a small dot of the other color, or catch them by hand while knitting.
• Jacquard checks the number of colors per row instead (up to 4 to start with), and has no float check.
• Slip stitch, mosaic and tuck & slip check how many times in a row a needle can tuck or slip, empty passes, and rows that mix tuck and slip.

The badge in the status bar shows the same verdict. Click it to bring the panel into view.

Size, repeats and gauge

Project in the toolbar (or a click on the size in the status bar) opens Project settings. These belong to this project only.

Size

• Panel: the whole piece, in stitches and rows. Size from a head measurement opens the hat calculator.
• Repeat tile: the motif you draw. Snap tile width to panel divisors only allows widths that fit the panel a whole number of times.
• Repeat: repeat the tile across, up, or both, and how it's lined up (for example centered). The number of repeats is shown underneath.
• Fit panel to whole tiles rounds the panel to a whole number of repeats.

Gauge

Enter the stitches and rows per 10 cm from a swatch. The app uses them to give sizes in centimeters, to draw stitches the right shape (Stitch shape), for the hat calculator, and for the text tool's Fit gauge.

Drawn rows / 10cm is for slip stitch and mosaic, where one drawn row takes several passes. If you leave it empty the app estimates it.

Yarn estimate and details

Yarn estimate shows roughly how much of each color the panel uses.

Details holds the project's name, technique (and jacquard backing), and free-form notes.

The library

Library in the toolbar holds things shared by every project.

The hat calculator

Calculators › Hat works out the panel size for a hat from a head measurement and your gauge.

Enter the head circumference in cm, the ease (how much smaller than the head the hat should be, in percent), the height, the number of rib rows and the seam stitches. Then press Set panel to W x H.

The panel is a rectangle. Crown shaping is done at the machine.

Saving and opening

Save (Ctrl+S) stores the project in the app. The button is highlighted while there are unsaved changes.

The File menu also has:

• Open project… (Ctrl+O): browse and search everything you've saved.
• Save as copy and New project.
• Import file…: load a .knitproj.json backup.
• Recent projects at the bottom.

Exporting files

You don't need to export anything to knit with the controller: the knit screen sends the design directly. Export is for sharing, printing, backups, and the original silver-reed-write software.

First choose the scope: the whole panel or one repeat tile.

The machine files are always Fair Isle files, because silver-reed-write only does single-bed Fair Isle. Exported images look exactly like the chart on screen, with row 1 (the cast-on edge) at the bottom.

Arranging the workspace

Each panel can be moved, folded up or hidden:

• Fold a panel by clicking its title bar. Click again to open it.
• Move a panel by dragging the dotted handle in its title bar to the left, right or bottom dock.
• Resize the side docks by dragging their inner edge.

The View menu switches the grid guides (grid lines, rulers, ghost repeats, repeat marks and the tool options bar) and each panel on or off. Reset layout puts everything back. A hidden panel can always be found again here.

The layout is remembered by your browser.

Keyboard shortcuts

In the designer

On the knit screen

Knitting Your first piece

Here's the whole process, from design to knitting. It assumes TinkrkniT is open and the controller is plugged in. Each step links to the section with more detail.

1. Draw the design. Pick colors in the Colors panel and draw with the tools. You draw one repeat tile and the app repeats it across the whole panel.
2. Check it. The Knittability panel should say Knits as drawn. If it lists rows to fix, click one to jump to it.
3. Look at it. The preview shows what the knitted fabric will look like.
4. Press Knit. The knit screen replaces the designer. Your design is frozen as a job, so later edits won't disturb it.
5. Connect. Press Connect and choose the controller. The log should say Controller firmware v2: change signals on.
6. Set the needle markers to match your point cams and press Markers are set to… (more).
7. Thread the yarns the yarn card asks for: Yarn A in feeder 1 and Yarn B in feeder 2 (more).
8. Start patterning, wait for the dot on the controller, and knit a pass. Keep going, one pass per row.
9. Change yarn when asked. The computer chimes, the controller's red and blue lights take turns, and its screen says which yarn to thread, for example YARN C (more). Change it, then carry on. The signal stops as soon as the carriage enters the pattern again.
10. Finish. At the last row the screen says DONE and the app plays a longer chime.

The knit screen

Press Knit in the toolbar (or K) when your design is ready. The designer is replaced by the knit screen. Your chart fills the left side and the cards on the right walk you through each pass.

The bar along the top

• Design goes back to the designer. The controller stays connected, so you can go back and forth freely.
• Machine: the knitting machine you're using. Only the Silver Reed SK840 is supported for now.
• Whole panel / Repeat tile: knit the whole design, or fill every needle between the markers with the repeat tile and keep going up forever. Repeat tile is handy for a test swatch or a piece of a different width.
• The design's name, technique and size.
• Connected / Not connected, and the Connect button.

The sidebar

1. Rows knitted: the big number, and the chart row that comes next. See Rows and the carriage.
2. Needle markers: where on the bed the pattern sits. See Setting the needle markers.
3. Carriage: which side the carriage is on and which way the next pass goes.
4. Yarns: what's in each feeder, what to change before this pass, and the next change coming up. See Yarns and changes.
5. Start patterning / Stop patterning.
6. Knitting options and the Controller log, which fold open. See Knitting options and log.

Start patterning stays greyed out until the markers are confirmed and the controller is connected. The note underneath says which is missing: Confirm the needle markers first or Connect to the controller first.

Connecting the controller

1. Plug the controller into the computer with a USB cable that carries data.
2. Press Connect in the top-right corner of the knit screen.
3. The browser lists the serial ports. Pick the controller (it usually has USB, CP210x or CH340 in its name) and press Connect.
4. The pill turns to Controller connected. Opening the connection restarts the controller, so its screen goes back to ROW 0.

The app then asks the controller which version of the firmware it's running, and the Controller log says one of:

Disconnect closes the connection. Stop patterning first.

Setting the needle markers

The needle markers say which needles on the bed the pattern covers. They use the numbers printed on the bed: L1–L100 left of center and R1–R100 right of center.

Setting them is easy to forget, so until you've confirmed them the card is open and highlighted, and you can't start patterning.

1. Choose where the pattern sits with Pattern: Left, Centered or Right. For a repeat tile it's Repeat from instead. Center on the bed puts it back in the middle.
2. Or type the needle numbers into Left marker and Right marker, choosing L or R for each. The strip below shows where that is on the bed.
3. Move the point cams on the machine to those needles.
4. Press Markers are set to… to confirm.

Select end needles knits both edge needles in feeder 2, so both yarns are caught at the edges.

Once confirmed, the card shrinks to show the range (for example L60 – R60). Press Change to move them. Any change has to be confirmed again.

If the panel is wider than the machine's bed, the card tells you.

Rows and the carriage

Rows knitted is the big number. It counts passes from 0, the same way the machine's own row counter does, so reset both together with Reset count.

Underneath, Next: chart row 4 of 160 is where you are in the design, with a progress bar.

• Row + and − Row (or the ↑ and ↓ keys) move one row. Back to row 1 starts again.
• You can also click a row on the chart to knit it next.

The Carriage card shows which side the carriage is on and which way the next pass goes. The app follows it as you knit. If it ever gets it wrong, press It's on the other side.

For every technique except Fair Isle, the card also says how to set the carriage, for example Carriage: Tuck buttons in.

Yarns and changes

On the knit screen, each color in your design gets a yarn letter, in the order they're first knitted: the first is Yarn A, the next Yarn B, and so on. The same letters appear on the controller's screen, so you always know which cone to reach for.

The yarn card shows:

• Feeder 1 – background and Feeder 2 – selected needles: what should be threaded now.
• Change yarn before this pass (with an amber outline) when the next pass needs something different, for example Feeder 2: Yarn B → Yarn C. On a one-yarn pass it also says which side the new yarn hangs, and whether to cut the old one or leave it parked.
• Carriage: the cam setting, and Change the carriage when that changes.
• Next change: the change after this one, and how many passes away it is.

When a change comes up

As the carriage finishes the pass before a change, three things happen together:

1. The computer plays a chime (a longer one when the panel is finished).
2. The controller's red and blue lights take turns, half a second each.
3. The controller's screen shows what to do instead of the needle count, for example YARN C.

Make the change, then knit on. The signal stops as soon as the carriage enters the pattern area. There's no need to press anything: the next row has already been sent. See Yarn and carriage changes for everything the controller can show.

Matching letters to your cones

Click All yarns at the bottom of the yarn card to see which letter knits each design color.

• Give two design colors the same letter to knit both from one cone.
• Click a feeder color chip to change the color shown for that yarn, for example to match what's really on the cone. This doesn't change your design.
• Reset yarns goes back to the design's colors and letters.

The letters and colors are remembered for the next job, as long as the design's palette hasn't changed.

Knitting options and log

Click Knitting options to open it.

The Controller log lists what the app and the controller have said to each other: loading the design, connecting, the firmware version, and the controller's status messages. It's the first place to look when something isn't working.

Editing the design mid-piece

When you press Knit, the design is frozen as a job. Editing the design afterwards never changes rows that are already queued.

To knit your changes, go back to the designer, edit, and press Knit again:

• If nothing has changed, you just go back to the knit screen.
• If it has changed and you haven't knitted anything yet, the new version replaces the old one.
• If you've already started knitting, a banner asks: Load the new design or Keep knitting this. Stop patterning before loading the new one.

The browser asks before closing the tab while you're patterning, so you can't lose your place by accident.

Setting up the controller

1. Open TinkrkniT in Chrome or Edge (see Getting the software).
2. Plug in. Connect the carriage cable to the controller, then connect the controller to your computer with a USB cable. The screen will show ROW 0.
3. Open the knit screen and connect. Press Knit in the app, then Connect, and pick the controller's USB connection. Make sure no other program is using that connection. See Connecting the controller.
4. Set your point cams. These are the two markers on the needle bed that tell the carriage where patterning starts and stops. Place them at the needles the knit screen shows (for example L60 and R60), so they cover exactly as many needles as your design is wide.
5. Wait for the dot. A small dot flashes in the top-left corner of the screen when a row arrives. Once you've seen it, make one pass with the carriage. Repeat for every row.

If you'd like to check everything before a real piece, push the carriage across the bed once with nothing loaded. The needle count on the screen should climb up to your design width. The controller uses this first pass to measure how wide your knitting is, so until you've done one pass it shows a plain count with no total.

What's on the box

Reading the Screen

This is the screen you'll see most of the time. Here are the main elements:

1. The dotA new row has just arrived from your computer.
2. The ! markSomething needs a look. See Controller problems.
3. The arrowShows which way the carriage is travelling. It's solid while you're patterning and an outline when you're not.
4. Row numberHow many rows you've knitted so far.
5. Needle countHow many needles you've passed in this row, out of the total. Between passes, this line shows the next yarn or carriage change instead.
6. Progress barFills up as you cross the bed.

What you'll see as you knit

Yarn and carriage changes

When TinkrkniT knows the next pass needs a different yarn or carriage setting, it tells the controller along with the row. While the carriage waits at the side, the controller then:

• Alternates the red and blue lights, half a second each (the small light on the circuit board blinks with the blue one).
• Replaces the needle count with what to do.

The signal stops when the carriage enters the pattern area (you've made the change and started knitting) or when the app cancels the row. While it's showing, the lights show the change rather than the red warning flash, but the ! stays on the screen, so you won't miss a warning.

This needs controller firmware version 2 and TinkrkniT. With older firmware, or other software, the controller simply knits and doesn't signal changes.

The rhythm of knitting

Every row follows the same four steps:

1. The row arrives. Your computer sends the next row and the dot blinks. If the row needs a yarn or carriage change, the lights start taking turns.
2. You push the carriage into the pattern area. The arrow turns solid, the needle count starts from 0, and any change signal stops.
3. The controller picks needles. As the carriage passes each needle, the controller tells it whether to select that one. The blue light flickers in time, and your computer shows live progress.
4. The carriage leaves the pattern area. The row counter goes up by one, and the computer sends the next row.

The button

Just one button does everything. (The BOOT button on the circuit board works the same way once the controller is running.)

A tap is a quick press (under half a second). If you tap a fifth time, it won't bounce you straight back out of diagnostics.

The lights

The two lights in the button above the screen show the most important thing going on right now. If more than one thing is happening, the one higher in this list wins.

Built-in safety

The needle selector in the carriage is a small electromagnet (a solenoid). It's meant to switch on in short bursts as the carriage passes each needle, and it can overheat if it stays on. The controller looks after this for you, so there's nothing to set up.

• It's off whenever nothing is happening. The selector is switched off at start-up, at the end of every row, and whenever no row is loaded.
• It switches off if the carriage stops mid-row. If the selector has been on for 3 seconds without a break, the controller switches it off, flashes the red light and shows SAFETY: OUT off.
• Damaged rows are never knitted. A row that arrives incomplete or garbled is thrown away and reported, and the pass knits plain.

The full list of safeguards is in How the controller protects your machine, in Controller Hardware.

The built-in test pattern

The controller can knit a pattern on its own. This is handy for checking that the carriage, cable and needle selector are all working. It makes a checkerboard of 3×3 squares: 3 needles selected, then 3 not, swapping every 3 rows.

1. Knit one plain pass first so the controller learns the width. Otherwise it assumes the maximum of 200 needles, and right-to-left rows won't line up.
2. Open the diagnostics screen (4 quick taps), then hold the button for 1 second. The bottom line says TEST MODE ON, and the T symbol appears on the knitting screen.
3. Tap once to go back to the knitting screen, then knit as normal.
4. To stop, open diagnostics again and hold for 1 second.

If a row arrives from your computer, test mode switches off by itself and the computer's row is used. The checkerboard follows the row counter, so resetting the counter restarts the squares.

The diagnostics screen

Tap the button 4 times quickly to open this screen. It shows the computer link, the carriage signals and the current row, in small text. It's the first place to look when the ! warning appears.

1. Computer linkLINK means data arrived in the last 15 seconds. idle means it's connected but quiet. none means nothing has arrived since power-up.
2. Carriage activityACTIVE if the carriage signals changed in the last 3 seconds, otherwise quiet.
3. Direction and camsWhich way you're travelling, and whether you're inside (IN) or outside (out) the pattern area.
4. Needles and outputNeedles counted this row, out of the length of the loaded row. Out:1 means the needle selector is being driven right now.
5. Pattern and rowsWhether a row is waiting (ready), there is none (none), or the test pattern is on (TEST). R: is rows knitted / rows received.
6. Signal checkLive readings from the carriage wires, explained below.
7. Last eventThe most recent thing that happened. It starts with ! instead of > while a warning is active.

Using the signal check line

The line starting K C D in g b shows the carriage's three wires. With the carriage still, you see their current state (0 or 1). Move the carriage slowly and watch them change:

• K (point cam) should switch to 1 as you pass the first point cam, and back to 0 at the second.
• C (clock) should flip once for every needle you pass.
• D (direction) should change when you reverse. 1 means moving left.
• in is the number of needle pulses inside the cams on the last pass. It should match your design width.
• g is the number of electrical noise spikes that were filtered out. If it keeps climbing, the wiring is picking up interference.
• b is the number of rows whose needle count changed unexpectedly.

If one of them never changes, check the carriage cable is pushed in fully at both ends. If it still doesn't change, the wiring needs a look (see Carriage signals and wiring).

What the status messages mean

These appear on the bottom line of the diagnostics screen. Most are also sent to the control software and show in the TinkrkniT Controller log. Rows marked with ! turn on the warning mark and the red light.

A warning stays on until the end of the next pass that finishes without a problem.

When the controller looks wrong

Most problems have a simple cause. Find what you're seeing below.

When TinkrkniT looks wrong

Carriage signals and wiring

The three carriage signals

• Clock: one pulse per needle as the carriage moves. The controller uses it to know which needle the selector is over.
• Point cam: tells the controller when the carriage is inside the patterning range set by the point cams.
• Direction: whether the carriage is travelling left or right.

Carriage connector (8-pin DIN)

Controller pin map (ESP32 DevKit)

The solenoid power switch (VDRIVE)

The carriage's 16 V solenoid supply (DIN pin 6, VDRIVE) isn't connected straight to the power supply. It goes through a small switching circuit, so the solenoid only gets power when the controller asks for it, and can't draw more than a safe current even if something goes wrong.

How the circuit works

1. Off by default. R1 (10 kΩ) holds the gate of Q1, the IRF9Z34 P-channel MOSFET, at the supply voltage, so the switch is off whenever nothing is driving it, including while the ESP32 is starting up or unplugged.
2. The ESP32 turns it on. When the DOB output (GPIO 26, 3.3 V) goes high, it drives Q2, a 2N3904 transistor, through R2 (4.7 kΩ). Q2 pulls Q1's gate down to ground, Q1 turns on, and 16.4 V flows towards the carriage. When DOB goes low, the switch turns off again.
3. Fuse. F1 is a self-resetting PPTC fuse rated at 0.75 A hold. If too much current flows, for example from a short in the cable, it heats up and cuts the current. It resets by itself once it has cooled down.
4. Peak and hold. R3 (10 Ω, 5 W) and C1 (100 µF, 25 V) sit side by side in the line. The moment the switch turns on, the empty capacitor lets a full burst of current through to snap the solenoid in. As it charges, the current settles to what the resistor allows: enough to hold the solenoid, but less than full power, so it runs cooler. C1's + side faces the supply.
5. Common ground. The 16.4 V supply, the ESP32 and the carriage (DIN pin 8) share one ground.

How the controller protects your machine

The needle selector (the solenoid) runs from 16 V. It's designed to switch on in short bursts as the carriage sweeps past each needle. If it stays on for a long time it gets hot, which can damage it. The controller guards against that in several ways.

What the cut-off looks like while you knit, and how to try the controller without solenoid power, is covered in Built-in safety.

How TinkrkniT talks to the controller

The app and the controller talk over USB serial at 115200 baud, using the byte protocol from silver-reed-write, plus two extra commands for the change signals.

1. Hello. When it connects (and again when the controller announces it has restarted), the app sends CMD_HELLO (0x10). Firmware that knows about change signals answers MSG_HELLO (0x10) followed by its version number (currently 2).
2. Pass info. Only once a version has arrived does the app send CMD_PASS_INFO (0x11) before each row. Older firmware would read the unfamiliar bytes as commands, so it is never sent to them.
3. The row follows as usual.

CMD_PASS_INFO

If both the yarn and cam flags are set, the screen alternates between them. Done outranks a yarn change, which outranks a cam change. The signal is cleared when the carriage enters the cams, or by CMD_CLEAR_ROW.

Specifications