Arduino Stuff

UART Passthrough

With an Arduino Nano in the header and the UART lines connected, anything on those lines should be passed through to the second serial port that shows up when you plug in your Jumperless.

(You can also set the config option [serial_1] print_passthrough = true; and have it print on both. Don't worry about the baud rate, the Jumperless senses what the host computer is set to and changes the speed accordingly.

Quick Connection Shortcuts

The shortcuts to connect D0 and D1 to the Jumperless's UART Tx and Rx is A to connect, and a to disconnect.

Automatic Flashing

It will even sense when Arduino IDE is trying to upload code and twiddle the reset lines to allow you to flash code with just a single USB cable going to your Jumperless.

Tip: You can also use Wokwi with the Jumperless Bridge app for flashing - no need to even have the Arduino IDE open

Commands from Routable UART

You can send commands to the Jumperless from your Arduino (or anything connected to the routable UART) by wrapping them in XML-style tags. The tags are stripped out and the command is executed - the Arduino never sees them come back.

Two Types of Tags

There are two flavors of command tags, depending on what you want to do:

<j> Tags - Raw Commands

These run exactly like you typed them in the main Jumperless menu. Use these for things like making connections with f, loading files, or any single-character menu command.

<p> Tags - Python Commands

These run MicroPython commands directly. Perfect for connect(), disconnect(), adc_get(), dac_set(), and all the other Python hardware functions. The <p> tag automatically prepends the > that normally tells the Jumperless "this is a Python command."

Supported Tag Names

Any of these work (use matching opening and closing tags):

Python Commands with <p> Tags

The <p> tag is the most powerful way to control your Jumperless from Arduino code. It gives you direct access to all the MicroPython hardware functions.

Basic Example

#define OPENJCOMMAND Serial.print("<p>");
#define CLOSEJCOMMAND Serial.println("</p>");

void setup() {
  Serial.begin(115200);
  delay(1500);  // Give Jumperless time to boot
}

void loop() {
  // Read voltage on ADC channel 0
  OPENJCOMMAND
  Serial.print("adc_get(0)");
  CLOSEJCOMMAND
  delay(100);

  // Read the response
  while(Serial.available() > 0) {
    char c = Serial.read();
    // Process the voltage reading...
  }
}

Full Example - ADC Scanning

This sketch connects ADC0 to different breadboard rows and reads the voltage at each one:

#define OPENJCOMMAND Serial.print("<p>");
#define CLOSEJCOMMAND Serial.println("</p>");

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
  Serial.begin(115200);
  delay(1500);
}

int lastNode = 8;
int node = 8;
unsigned long delayTime = 60;

void loop() {
  digitalWrite(LED_BUILTIN, HIGH);
  delay(delayTime);

  node++;
  if (node > 60) {
    node = 1;
  }

  // Disconnect from previous node
  OPENJCOMMAND
  Serial.print("disconnect( ADC0," + String(lastNode) + ")");
  CLOSEJCOMMAND
  delay(delayTime);

  // Connect to new node
  OPENJCOMMAND
  Serial.print("connect(ADC0 ," + String(node) + ")");
  CLOSEJCOMMAND
  delay(delayTime);

  // Read the voltage
  OPENJCOMMAND
  Serial.print("adc_get(0)");
  CLOSEJCOMMAND
  delay(delayTime);

  // Read response from Jumperless
  char response[30] = {0};
  int idx = 0;
  while(Serial.available() > 0 && idx < 29) {
    response[idx++] = Serial.read();
    delay(5);
  }

  Serial.println(response);
  Serial.print("num chars read = ");
  Serial.println(idx);
  Serial.flush();

  lastNode = node;
  digitalWrite(LED_BUILTIN, LOW);
}

Available Python Functions

Here are the most useful functions you can call with <p> tags:

// Connections
"connect(1, 30)"              // Connect breadboard rows
"connect(D13, TOP_RAIL)"      // Connect Arduino pin to power
"disconnect(ADC0, 15)"        // Remove a connection
"nodes_clear()"               // Clear ALL connections

// Analog I/O
"adc_get(0)"                  // Read voltage (channels 0-4)
"dac_set(0, 3.3)"            // Set DAC output voltage
"dac_set(TOP_RAIL, 5.0)"     // Set rail voltage

// Digital I/O
"gpio_set(1, True)"          // Set GPIO high
"gpio_set(1, False)"         // Set GPIO low
"gpio_get(2)"                // Read GPIO state

// Current sensing
"ina_get_current(0)"         // Read current in amps
"ina_get_voltage(0)"         // Read shunt voltage

See the MicroPython API Reference for the complete list.

Raw Commands with <j> Tags

Use <j> tags when you want to send menu commands - the same ones you'd type in the serial terminal.

Example - Making Connections

#define OPENJCOMMAND Serial.print("<j>");
#define CLOSEJCOMMAND Serial.println("</j>");

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
  Serial.begin(115200);
  delay(1500);
}

int node1 = 1;
int node2 = 8;
unsigned long delayTime = 60;

void loop() {
  digitalWrite(LED_BUILTIN, HIGH);
  delay(delayTime);

  node1++;
  node2++;
  if (node1 > 60) node1 = 1;
  if (node2 > 60) node2 = 1;

  // Use the 'f' command to make a connection
  // Format: f <node1>-<node2>
  OPENJCOMMAND
  Serial.print("f " + String(node1) + "-" + String(node2) + "\n");
  CLOSEJCOMMAND
  delay(delayTime);

  // Read any response
  char response[30] = {0};
  int idx = 0;
  while(Serial.available() > 0 && idx < 29) {
    response[idx++] = Serial.read();
    delay(5);
  }

  Serial.println(response);
  digitalWrite(LED_BUILTIN, LOW);
}

Useful Raw Commands

Tips and Gotchas

Timing

The Jumperless needs a little time to process each command. A delay of 40-100ms between commands is usually safe. If you're seeing weird behavior, try increasing the delay.

Response Reading

Commands often return data (like adc_get() returning a voltage). Make sure to read the Serial buffer after sending commands, or it'll fill up and cause issues.

Startup Delay

Add a delay(1500) in your setup() to give the Jumperless time to fully boot before sending commands.

Flashing Your Arduino

Just use the Arduino IDE normally - select the second serial port that shows up (the one labeled with "port3" or similar), and upload. The Jumperless automatically handles the reset timing.

Which Tag to Use?

• Use <p> for anything that's a Python function: connect(), adc_get(), dac_set(), etc.
• Use <j> for menu commands: f, x, n, s, etc.

Wokwi Integration

If you're using the Jumperless Wokwi Bridge, you can flash your Arduino directly from Wokwi simulations - the bridge handles all the communication for you.