aschuma / esp32_ssd1306_metaefa

This MicroPython code, executed on an ESP32 OLED SSD1306 board, displays departure tables by utilizing the VVS Rest API (META EFA)

                                                                                
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The aim of this project is to display the departure data of one or more VVS stations (Haltestellenmonitor) on an ESP32 microcontroller equipped with an Oled SSD1306 display. VVS is the Stuttgart public transport system. VVS provides the current timetable of relevant stations by a public available REST endpoint. Micropython is the programming language of choice for this project.

Here is what you get when you deploy the application on your ESP32 board:

The top line contains the current time. The other lines hold the tram/bus line number, the departure time, the delay and the short name of the station (RH, SMi). (The relevant tram/bus lines and stations are configurable within a configuration resource)

Please note that the hosted version of the public REST endpoint (metaEFA) used by this project is not available anymore. Information on hosting a MetaEFA server yourself can be found at https://github.com/opendata-stuttgart/metaEFA.

Links:

• http://www.vvs.de/
• https://github.com/opendata-stuttgart/metaEFA
• https://www.espressif.com/en/products/socs/esp32
• https://www.aliexpress.com/item/Lolin-ESP32-OLED-wemos-for-Arduino-ESP32-OLED-WiFi-Modules-Bluetooth-Dual-ESP-32-ESP-32S/32807531243.html
• http://micropython.org/

Onboarding

This is just a brief description of what steps have to be performed to enable the development of this application. Please consult Google to get in-depth details.

Prepare development infrastructure

• Install the USB driver to enable board access: https://www.silabs.com/products/development-tools/software/usb-to-uart-bridge-vcp-drivers
• Install python 3.x
• Clone the repository

  git clone https://github.com/aschuma/esp32_ssd1306_metaefa.git
  

• Create a virtual environment, you may obtain more information about the steps below here: http://docs.python-guide.org/en/latest/dev/virtualenvs/

  cd esp32_ssd1306_metaefa/
  virtualenv py3 -p $(which python3)
  source py3/bin/activate
  

• Install development tools (ampy, rshell)  

  pip3 install -r requirements.txt 
  

Micropython - prepare the ESP32 board

• Download the latest ESP32 micropython image from https://micropython.org/download
• Prepare the board

  esptool.py --port /dev/cu.SLAB_USBtoUART flash_id
  esptool.py --port /dev/cu.SLAB_USBtoUART erase_flash
  esptool.py --port /dev/cu.SLAB_USBtoUART write_flash -z 0x1000 <path-to-downloaded-image>
  
  

Micropython - check board access

• The subsequent command is for MacOS only. Similar tools are available for Linux and Windows.

  screen /dev/cu.SLAB_USBtoUART 115200
  

  After that, you will be connected to the micropython shell running on the board. You may leave the shell by typing Ctrl-A, K and y.
• File explorer

  rshell -p /dev/cu.SLAB_USBtoUART
  

  The files on the board should be available locally at /pyboard on your dev machine. You may copy files to the board by using the cp command. More details are available here: https://github.com/dhylands/rshell

Please be aware that you can not use multiple shells simultaneously to the access the board.

Deployment

• Copy src/config.py.template to src/config.py and adjust at least the wifi settings.
• Copy recursively all files of src to the root directory of the board using the rshell tool or the ampy tool.
  • https://github.com/dhylands/rshell
  • https://github.com/adafruit/ampy
• The board should reboot itself. If not unplug the USB cord and plug it back again.
• In case of problems to connect to the board via screen /dev/cu.SLAB_USBtoUART 115200   press CTRL-C and CTRL-D to trigger a reboot. Then you should see some log messages.

Finally

Be aware that my primary coding language is not python. So please forgive me my bad coding style. I'm still learning python and ESP32 development.

Please feel free to issue a bug report or submit a PR. Any helping hand is welcome.

esp32_ssd1306_metaefa's Issues

Include lightway json parser

ui - boot - provide progress bar

Provide configuration resource

cet calculation - enhancements

• The summer time interval bounds must be adjusted to UTC
• Provide intervals for 2020, 2021, ...

build/unit testing - enable infrastructure

ui - provide delta minutes to departure time too

ui - more spacing

ui - define abstract ui model and provide render methods

ui - error - provide code to signal errors

Meta EFA API REST endpoint broken since 2018-12

opendata-stuttgart/metaEFA#20

ssd1306 - observed once: ENODEV 19 /* No such device */

Observed once: (self healing, recovered itself)
Problems occurred while refreshing UI

OSError: [Errno 19] ENODEV
Traceback (most recent call last):
  File "timer.py", line 15, in <lambda>
  File "main.py", line 85, in <lambda>
  File "main.py", line 42, in paint
  File "ssd1306.py", line 76, in invert
  File "ssd1306.py", line 104, in write_cmd
OSError: [Errno 19] ENODEV
Traceback (most recent call last):
  File "timer.py", line 15, in <lambda>
  File "main.py", line 85, in <lambda>
  File "main.py", line 42, in paint
  File "ssd1306.py", line 76, in invert
  File "ssd1306.py", line 104, in write_cmd
OSError: [Errno 19] ENODEV
...

#define ENODEV 19 /* No such device */

In addition the active rest service indicator is shown twice (now also on top of the screen)

cet - ensure periodical ntp sync or reboot esp32 at 3:15 am

wifi - Reconnect to WiFi when WiFi is available again

ui - refresh ui periodically so that we can include a clock

service - departure ordering

The order returned be efa rest is the planed departure time...

• 21:56 S1 03 SMitte
• 21:54 U2 00 SMitte
• 22:03 S2 00 SMitte
• 22:08 S1 00 SMitte
• 22:09 U2 00 SMitte
• 22:14 S3 01 SMitte
  ... this must be adusted by the delay time (3rd column)

UTC to CET

network - provide support for multiple wifi environments

The device should work when is is moved from my home zone to my business location.

ssd1306 - add driver libraries

• Add ssd1306 libraries.
• Check whether a driver exists supporting more fonts
• Provide boot code to initialise the display

Single station - display destination stations

rest - enable REST interface for debugging purpose

code: timer.js - IndexError: list index out of range

since esp32-20190125-v1.10

Traceback (most recent call last):
 File "timer.py", line 11, in 
 File "main.py", line 88, in 
 File "main.py", line 71, in paint
IndexError: list index out of range
Traceback (most recent call last):

documentation - provide developer onboarding / readme.md

efa - use the stream of the underlying http connection and pass the bytes directly to the json parser

esp32_ssd1306_metaefa/efa.py

Line 51 in 9e0e13c

data = io.StringIO(request.text)

Background:

My esp32 device was running out of memory when creating a json object directly from response body. Unfortunately there is not yet an api parameter to limit the response of the efa api. See opendata-stuttgart/metaEFA#15

The json stream parser stuff itself is a workaround for that. I really would like to remove that json stream parsing to reduce the overall complexity.

cet_time - get rid of ugly python/micropython compatibility stuff

Migrate to VVS API (http://www3.vvs.de/vvs/widget/XML_DM_REQUEST?)

service - processing of efa service response is very slow

efa json rest response parsing is currently very slow (25 seconds, two efa rest requests, 20k data to process for each call)

call metaefa rest api

call metaefa
filter result (station, number, destination, minutes to walk to station) using naya

see https://gist.github.com/aschuma/b9f7d387d6c342704fafc62f65255b39

service - run background to fetch rest data periodically