Crypto-Display

The ticker displays one cryptocurrency at a time, showing: symbol, price, and 24hr % change.

This document breaks down processes used to call live market data, parse it, and post it to the board (in technical terms). For a simplified logic breakdown please check out my Medium article.

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How it works:

Components:

• LED Matrix Dispay (64 by 32 pixels, 3mm pitch)
• Arduino ESP8266 Controller

Picking Symbols:

This project uses the CoinMarketCap API to fetch live market data. Before it's called, we need to initialize SYMBOLS[] with the cryptos we want data on. For example:

SYMBOLS = ['BTC', 'ETH', 'NEAR', 'AMPL']

MatrixPortal class object (matrixportal module):

Using the matrixportal module from Adafruit's library, we create an class object called MatrixPortal. We can use this object to both call data and set the text on the display. We'll initialize our object with:

• DATA_SOURCE -- URL which has been concatenated with our list of symbols
• HEADERS -- the API key tied to our CMC account
• Formatting for our text

Important methods:

.fetch() -- will fetch JSON data from the object's data source, which is then stored in the variable r

.set_text(string) -- will show the passed string on the display

Display Class:

We create a class called Display to store our parsed data, and create methods for changing the display.

• COUNTER -- pointer used for iterating through our data one symbol at a time
• SYM_DICT -- dictionary of dictionaries (key: COUNTER, value: latest data on a single crypto)

Important methods:

.refresh() -- Refreshes SYM_DICT with new data: Uses matrixportal.fetch() to get new JSON data, parses it into SYMBOL, PRICE, and DAY_CHANGE and stores it in SYM_DICT under the COUNTER, increments COUNTER, then does it again with the next crypto until it reaches the end of our list.

.next() and .prev() -- increments up and down respectively through the list of symbols

.post() -- Puts data on the display: Creates a string from the data indexed at the current value of COUNTER, uses matrixportal.set_text(string) to display it.

Loop:

When the device boots, it begins a loop to cycle through all of the symbols to display. They are set to cycle every 5 seconds, and the data refreshes every 5 minutes.