Escher — The world’s first cloud-controlled Etch-a-Sketch

The Escher web interface.

Design considerations

Hardware design

The Adafruit HUZZAH32 — Image from
The custom power distribution board for Escher. Totally not necessary if you want to use two power supplies instead.

3D printed base

Designing the Escher base in FreeCAD.
Rear view, showing electronics.

The software

The web client and the HUZZAH32 communicate via Firebase.

Web client design

G-code support

Arduino firmware

Adafruit_MotorShield AFMS = Adafruit_MotorShield();
Adafruit_StepperMotor *myStepper1 = AFMS.getStepper(200, 1);
Adafruit_StepperMotor *myStepper2 = AFMS.getStepper(200, 2);
void forwardstep1() {
myStepper1->onestep(BACKWARD, SINGLE);
void backwardstep1() {
myStepper1->onestep(FORWARD, SINGLE);
void forwardstep2() {
myStepper2->onestep(BACKWARD, DOUBLE);
void backwardstep2() {
myStepper2->onestep(FORWARD, DOUBLE);
AccelStepper stepper1(forwardstep1, backwardstep1);
AccelStepper stepper2(forwardstep2, backwardstep2);
MultiStepper mstepper;
#define BACKLASH_X 10
#define BACKLASH_Y 15
// Move to the given position, specified in stepper units.
void EscherStepper::moveTo(long x, long y) {
// Figure out if we're reversing direction in x or y axes.
long dirx = x - last_x_;
if (dirx > 0) {
dirx = 1;
} else if (dirx < 0) {
dirx = -1;
long diry = y - last_y_;
if (diry > 0) {
diry = 1;
} else if (diry < 0) {
diry = -1;
if (dirx != dir_x_) {
cur_backlash_x_ += (dirx * BACKLASH_X);
if (diry != dir_y_) {
cur_backlash_y_ += (diry * BACKLASH_Y);
long target[2] = {x + cur_backlash_x_, y + cur_backlash_y_};
last_x_ = x;
last_y_ = y;
// Don't want to add backlash when transitioning from x -> 0 -> x
if (dirx != 0) {
dir_x_ = dirx;
if (diry != 0) {
dir_y_ = diry;
// Download the given URL and save it to flash storage.
// Returns true if successful, false otherwise.
bool downloadGcode(const char* url) {
int responseCode = http.GET();
if (responseCode <= 0) {
Serial.printf("[downloadGcode] failed, error: %s\n",
return false;
File outFile ="/data.gcd", FILE_WRITE);
int bytesRead = http.writeToStream(&outFile);
if (bytesRead < 0) {
return false;
} else {
return true;

Stuff that worked, stuff that didn’t




VP of Engineering at, building compilers for fast AI. Ex-Google engineering director, Ex-Apple. Systems hacker and drinker of beer.

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Matt Welsh

Matt Welsh

VP of Engineering at, building compilers for fast AI. Ex-Google engineering director, Ex-Apple. Systems hacker and drinker of beer.

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