show current yen/dollar exchange rate on LCD

ESP32-Micropython-HTTP-GET-sample.py

from micropython import const
from machine import Pin, I2C
import time

CLEAR_DISPLAY       = const(0x01)
RETURN_HOME         = const(0x02)
SET_ENTRY_MODE      = const(0x04)
DISPLAY_ON          = const(0x0C)
FUNCTION_SET        = const(0x20)
OSC_FREQUENCY       = const(0x10)
POW_ICON_CONTRAST   = const(0x50)
FOLLOWER            = const(0x60)
SET_CONTRAST        = const(0x70)
SET_DDRAM_ADDR      = const(0x80)

class ST7032i(object):

    def __init__(self, i2c, addr=0x3e):
        self.i2c = i2c
        self.addr = addr
        self.buf = bytearray(2)
        self.init_display()

    def write_cmd(self, cmd):
        self.buf[0] = 0x00
        self.buf[1] = cmd
        self.i2c.writeto(self.addr, self.buf)

    def write_data(self, char):
        self.buf[0] = 0x40
        self.buf[1] = char
        self.i2c.writeto(self.addr, self.buf)

    def init_display(self):
        for cmd in (
            # data is 8 bits | 2 lines mode
            FUNCTION_SET | 0x10 | 0x08,
            # select Instruction table 1
            FUNCTION_SET | 0x10 | 0x08 | 0x01,
            # BS=1 (1/4 bias), OSC frequency=183Hz
            OSC_FREQUENCY | 0x08 | 0x04,
            # ICON on, Booster on, Contrast(upper 2bits) = 10
            POW_ICON_CONTRAST | 0x08 | 0x04 | 0x02,
            # Contrast(lower 4bits) = 1000
            SET_CONTRAST | 0x08,
            # Follower on, voltage regulator amplified ratio = 3.33
            FOLLOWER | 0x08 | 0x03
            ):
            self.write_cmd(cmd)
        time.sleep(0.2)
        for cmd in (
            DISPLAY_ON,
            CLEAR_DISPLAY,
            # Left to right, no shift
            SET_ENTRY_MODE | 0x02
            ):
            self.write_cmd(cmd)

    def clear(self):
        self.write_cmd(CLEAR_DISPLAY)

    def set_cursor(self, row, col=0):
        row = min(0x3f, max(0, row))
        col = min(1, max(0, col))
        self.write_cmd(SET_DDRAM_ADDR | row + (0x00, 0x40)[col])

    def print_str(self, s):
        for c in s:
            self.write_data(ord(c))

def wlan_connect(ssid='SSID', password='PASSWD'):
    import network
    wlan = network.WLAN(network.STA_IF)
    if not wlan.active() or not wlan.isconnected():
        wlan.active(True)
        print('connecting to:', ssid)
        wlan.connect(ssid, password)
        while not wlan.isconnected():
            pass
    
def http_get(url):
    import socket
    _, _, host, path = url.split('/', 3)
    addr = socket.getaddrinfo(host, 80)[0][-1]
    s = socket.socket()
    s.connect(addr)
    s.send(bytes('GET /%s HTTP/1.0\r\nHost: %s\r\n\r\n' % (path, host), 'utf8'))
    while True:
        line=s.readline()
        if len(line.rstrip()) == 0:
            break
    line = ""   
    while True:
        data = s.recv(100)
        if data:
            line = line + str(data, 'utf8')
        else:
            break
    s.close()
    return line

def main():
    import ujson
    wlan_connect()
    i2c = I2C(scl=Pin(21), sda=Pin(22), freq=400000)
    i2c.scan() # workaround for SPLC792-I2C-M communication problem
    lcd = ST7032i(i2c)
    content = http_get('http://api.fixer.io/latest?base=USD&symbols=JPY')
    parsed = ujson.loads(content)
    lcd.set_cursor(0, 0);
    lcd.print_str(parsed["date"]);
    lcd.set_cursor(0, 1);
    lcd.print_str("JPY/" + parsed["base"] + ": " + str(parsed["rates"]["JPY"]))

http://blog.boochow.com/article/453856306.html