Notecard Interfaces

Requests can be issued to the Notecard over USB, UART, or I2C. The Serial UART interface is fixed at a baud rate of 9600, with eight data bits, no parity bit, and one stop bit (9600/N-8-1).

The Notecard I2C interface is available at address 0x17, but can be reconfigured using a card.io request. This interface implements a straightforward serial over I2C protocol.

Using the Notecard Interface with a Firmware Library

The simplest way to initiate a connection with the Notecard from firmware is with one of our firmware libraries. Using this approach, you can initialize the Notecard over the appropriate interfacing using a few lines of code. For instance, with Serial:

COPY
#include <Notecard.h>

Notecard notecard;
notecard.begin(Serial1, 9600);

COPY
import notecard
import serial

port = serial.Serial("/dev/serial0", 9600)
card = notecard.OpenSerial(port)

Or with I2C:

COPY
#include <Notecard.h>

Notecard notecard;
notecard.begin();

COPY
import notecard
from periphery import I2C
port = I2C("/dev/i2c-1")

card = notecard.OpenI2C(port, 0, 0)

Using the Notecard Interface with Simple Serial I/O

warning

If NOT using a Notecard firmware library, you may unintentionally send requests to the Notecard so fast that you overflow the 1500 byte buffer used to receive data (whether it be I2C, Serial, or UART). The solution is to pause 250 ms after every 250 bytes sent and ensure the total size of each NDJSON object sent is no more than 8KB.

Alternatively, it's possible to manually communicate with the Notecard over Serial in firmware using language-equivalent print() and read() functions.

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#define txRxPinsSerial Serial1

// Initialize the Notecard
txRxPinsSerial.begin(9600);
txRxPinsSerial.println("\n");

// Send a hub.set request
txRxPinsSerial.println("{\"req\":\"hub.set\",\"product\":\""
                        myProductID "\"}");

COPY
import json
import serial

serial = serial.Serial('/dev/ttyS0', 9600)
serial.write(b'\n')

req = {"req": "hub.set"}
req["product"] = myProductID
serial.write(bytearray(json.dumps(req), 'utf8'))
serial.write(b'\n')

The Notecard Serial-over-I2C Protocol

If, on the other hand, you wish to use I2C without one of our firmware libraries, you'll need to write your own logic for writing to and reading from the bus. Your approach will vary from one language to the next, but you should use the existing implementations and the Serial-over-I2C Protocol Guide for reference.