PTV Station Screen with a Wemos D1 Mini

README.md

PTV Station Screen with a Wemos D1 Mini

Intro

This is an implementation of a basic PTV departures screen using the PTV API, a Wemos D1 Mini, MicroPython and an OLED shield.

Getting Started

If you want to use it there's a few things you'll need to do:

• Connect the D1 mini to your WiFi network (instructions in the documentation)
• Set your API key and devId (more info here)
• Set the stopId you're interested in, which you can find by playing around with the API here - exact procedure is left as an exercise for the reader ;)

To-do (maybe one day)

• Show the last updated date as local time. This is a bit challenging because it requires knowing the timezone, which requires a more involved date library.

dates.py

import utime, ure

months = {"Jan": 1, "Feb": 2, "Mar": 3, "Apr": 4, "May": 5, "Jun": 6, "Jul": 7, "Aug": 8, "Sep": 9, "Oct": 10, "Nov": 11, "Dec": 12}

# e.g. Fri, 10 Aug 2018 02:26:24 GMT
current_date_re = ure.compile('^\w+, (\d+) (\w+) (\d+) (\d+):(\d+):(\d+) GMT$')
def parse_current_date(date_str):

    dateparts = current_date_re.match(date_str)

    return utime.mktime((
        int(dateparts.group(3)), # year
        months[dateparts.group(2).decode()], # month
        int(dateparts.group(1)), # day
        int(dateparts.group(4)), # hour
        int(dateparts.group(5)), # min
        int(dateparts.group(6)), # sec
        None,
        None
    ))

# e.g. 2018-08-10T03:54:00Z
dep_date_re = ure.compile('^(\d+)-(\d+)-(\d+)T(\d+):(\d+):(\d+)Z$')
def parse_dep_date(date_str):

    dateparts = dep_date_re.match(date_str)

    return utime.mktime((
        int(dateparts.group(1)), # year
        int(dateparts.group(2)), # month
        int(dateparts.group(3)), # day
        int(dateparts.group(4)), # hour
        int(dateparts.group(5)), # min
        int(dateparts.group(6)), # sec
        None,
        None
    ))

hmac.py

"""HMAC (Keyed-Hashing for Message Authentication) Python module.

Implements the HMAC algorithm as described by RFC 2104.

This is modified from the original MicroPython HMAC library to
remove references to the copy function (seems that isn't supported).
"""

#from _operator import _compare_digest as compare_digest
import uhashlib as _hashlib
PendingDeprecationWarning = None
RuntimeWarning = None

trans_5C = bytes((x ^ 0x5C) for x in range(256))
trans_36 = bytes((x ^ 0x36) for x in range(256))

def translate(d, t):
    return bytes(t[x] for x in d)

# The size of the digests returned by HMAC depends on the underlying
# hashing module used.  Use digest_size from the instance of HMAC instead.
digest_size = None



class HMAC:
    """RFC 2104 HMAC class.  Also complies with RFC 4231.

    This supports the API for Cryptographic Hash Functions (PEP 247).
    """
    blocksize = 64  # 512-bit HMAC; can be changed in subclasses.

    def __init__(self, key, msg = None, digestmod = None):
        """Create a new HMAC object.

        key:       key for the keyed hash object.
        msg:       Initial input for the hash, if provided.
        digestmod: A module supporting PEP 247.  *OR*
                   A hashlib constructor returning a new hash object. *OR*
                   A hash name suitable for hashlib.new().
                   Defaults to hashlib.md5.
                   Implicit default to hashlib.md5 is deprecated and will be
                   removed in Python 3.6.

        Note: key and msg must be a bytes or bytearray objects.
        """

        if not isinstance(key, (bytes, bytearray)):
            raise TypeError("key: expected bytes or bytearray, but got %r" % type(key).__name__)

        if digestmod is None:
            digestmod = _hashlib.md5

        if callable(digestmod):
            self.digest_cons = digestmod
        elif isinstance(digestmod, str):
            self.digest_cons = lambda d=b'': _hashlib.new(digestmod, d)
        else:
            self.digest_cons = lambda d=b'': digestmod.new(d)

        self.outer = self.digest_cons()
        self.inner = self.digest_cons()
        self.digest_size = 20 # force just for this

        if hasattr(self.inner, 'block_size'):
            blocksize = self.inner.block_size
            if blocksize < 16:
                blocksize = self.blocksize
        else:
            blocksize = self.blocksize

        # self.blocksize is the default blocksize. self.block_size is
        # effective block size as well as the public API attribute.
        self.block_size = blocksize

        if len(key) > blocksize:
            key = self.digest_cons(key).digest()

        key = key + bytes(blocksize - len(key))
        self.outer.update(translate(key, trans_5C))
        self.inner.update(translate(key, trans_36))
        if msg is not None:
            self.update(msg)

    @property
    def name(self):
        return "hmac-" + self.inner.name

    def update(self, msg):
        """Update this hashing object with the string msg.
        """
        self.inner.update(msg)

    def _current(self):
        """Return a hash object for the current state.

        To be used only internally with digest() and hexdigest().
        """
        h = self.outer
        h.update(self.inner.digest())
        return h

    def digest(self):
        """Return the hash value of this hashing object.

        This returns a string containing 8-bit data.  The object is
        not altered in any way by this function; you can continue
        updating the object after calling this function.
        """
        h = self._current()
        return h.digest()

def new(key, msg = None, digestmod = None):
    """Create a new hashing object and return it.

    key: The starting key for the hash.
    msg: if available, will immediately be hashed into the object's starting
    state.

    You can now feed arbitrary strings into the object using its update()
    method, and can ask for the hash value at any time by calling its digest()
    method.
    """
    return HMAC(key, msg, digestmod)

main.py

import machine, ssd1306, urequests2 as requests, ptv_api, dates, utime
i2c = machine.I2C(-1, machine.Pin(5), machine.Pin(4))
oled = ssd1306.SSD1306_I2C(64, 48, i2c)


def update():
    oled.fill(0)

    oled.show()

    stop = "123" #TODO: change to the stopId you're interested in
    (current_date, data) = ptv_api.get("/v3/departures/route_type/0/stop/{stopId}/route/4?direction_id=1&max_results=2".format(stopId=stopId)

    y_offset = 0

    for departure in data['departures']:
        
        dep_date = dates.parse_dep_date(departure['estimated_departure_utc'])
        (_, run_details) = ptv_api.get('/v3/runs/' + str(departure['run_id']))
        run = run_details['runs'][0]
        dest = 'Flinders' if 'Flinders' in run['destination_name'] else 'CityLoop' 
        express = run['express_stop_count'] > 0
        print(dest + " in " + str(round((dep_date - current_date) / 60)) + ", express=" + str(express))
        
        mins_away = str(round((dep_date - current_date) / 60))
        oled.text(dest, 0, y_offset)
        
        dist = mins_away + "min" + ("" if mins_away == "1" else "s")
        if mins_away == "0":
            dist = "now"
        
        oled.text(dist, 0, y_offset + 8)
        if express:
            oled.text('E', 55, y_offset + 8)

        y_offset += 18
        oled.hline(0, y_offset - 2, 999, 0xffff)

    (year, month, day, hour, minute, second, _, _) = utime.localtime(current_date)
    oled.text("Upd{hour:02}:{minute:02}".format(hour=hour, minute=minute), 0, 40)

    oled.show()



tim = machine.Timer(-1)
tim.init(period=60000, mode=machine.Timer.PERIODIC, callback=lambda t:update())

update()

ptv_api.py

import urequests2 as requests, hmac, ubinascii, dates
from uhashlib import sha1

# TODO: get these from PTV
# https://static.ptv.vic.gov.au/PTV/PTV%20docs/API/1475462320/PTV-Timetable-API-key-and-signature-document.RTF
api_key = b"api_key" 
devid = 123

def get(base_url):
    raw = base_url + ('&' if ('?' in base_url) else '?') + 'devid={devid}'.format(devid=devid)

    hashed = hmac.new(api_key, raw, sha1)
    signature = ubinascii.hexlify(hashed.digest()).decode()

    response = requests.get('http://timetableapi.ptv.vic.gov.au' + raw + '&signature=' + signature)
    data = response.json()
    current_date = dates.parse_current_date(response.date)
    return (current_date, data)

train-timetable-screen.jpg

urequests2.py

# This is a modified version of the MicroPython requests
# library which returns the Date header from the response 
# if it was present. This is my clever trick for knowing
# the time on a device without a RTC ;)

import usocket

class Response:

    def __init__(self, f):
        self.raw = f
        self.encoding = "utf-8"
        self._cached = None

    def close(self):
        if self.raw:
            self.raw.close()
            self.raw = None
        self._cached = None

    @property
    def content(self):
        if self._cached is None:
            try:
                self._cached = self.raw.read()
            finally:
                self.raw.close()
                self.raw = None
        return self._cached

    @property
    def text(self):
        return str(self.content, self.encoding)

    def json(self):
        import ujson
        return ujson.loads(self.content)


def request(method, url, data=None, json=None, headers={}, stream=None):
    try:
        proto, dummy, host, path = url.split("/", 3)
    except ValueError:
        proto, dummy, host = url.split("/", 2)
        path = ""
    if proto == "http:":
        port = 80
    elif proto == "https:":
        import ussl
        port = 443
    else:
        raise ValueError("Unsupported protocol: " + proto)

    if ":" in host:
        host, port = host.split(":", 1)
        port = int(port)

    ai = usocket.getaddrinfo(host, port, 0, usocket.SOCK_STREAM)
    ai = ai[0]

    s = usocket.socket(ai[0], ai[1], ai[2])
    try:
        s.connect(ai[-1])
        if proto == "https:":
            s = ussl.wrap_socket(s, server_hostname=host)
        s.write(b"%s /%s HTTP/1.0\r\n" % (method, path))
        if not "Host" in headers:
            s.write(b"Host: %s\r\n" % host)
        # Iterate over keys to avoid tuple alloc
        for k in headers:
            s.write(k)
            s.write(b": ")
            s.write(headers[k])
            s.write(b"\r\n")
        if json is not None:
            assert data is None
            import ujson
            data = ujson.dumps(json)
            s.write(b"Content-Type: application/json\r\n")
        if data:
            s.write(b"Content-Length: %d\r\n" % len(data))
        s.write(b"\r\n")
        if data:
            s.write(data)

        l = s.readline()
        #print(l)
        l = l.split(None, 2)
        status = int(l[1])
        reason = ""
        date = ""
        if len(l) > 2:
            reason = l[2].rstrip()
        while True:
            l = s.readline()
            if not l or l == b"\r\n":
                break
            if l.startswith(b"Transfer-Encoding:"):
                if b"chunked" in l:
                    raise ValueError("Unsupported " + l)
            elif l.startswith(b"Location:") and not 200 <= status <= 299:
                raise NotImplementedError("Redirects not yet supported")
            elif l.startswith(b"Date:"):
                date=l[6:-2]
    except OSError:
        s.close()
        raise

    resp = Response(s)
    resp.status_code = status
    resp.reason = reason
    resp.date = date
    return resp


def head(url, **kw):
    return request("HEAD", url, **kw)

def get(url, **kw):
    return request("GET", url, **kw)

def post(url, **kw):
    return request("POST", url, **kw)

def put(url, **kw):
    return request("PUT", url, **kw)

def patch(url, **kw):
    return request("PATCH", url, **kw)

def delete(url, **kw):
    return request("DELETE", url, **kw)