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I am trying to chart real time data from a Raspberry Pi to a web server. In this case I am using dash (https://dash.plot.ly/live-updates) to do this. I am currently testing my dash web browser on static data on my mac, and so far it works just fine. Aside from a deprecation message about plotly, and a No Handlers could be found for logger "werkzeug", it works completely fine. BUT when I try to run the exact same script on my raspberry Pi, I hit problems.

On my raspberry Pi, the web server runs, I can open it up on localhost, but the charts are empty!!! I get no error messages or reasons why this is happening!

On Raspberry Pi

Whereas I need it to look like this. Below is what appears when I run the exact same script on my desktop.

Any Dash/Plotly or graphing wizards know why this could be happening?? Thank you!!!

enter image description here

Here is my entire script:

import os, sys
from pathlib import Path
currDir = Path(os.path.abspath(__file__))
_rootDir = currDir.parent.parent
# _dataDir = str(_rootDir / 'GridBallast-RaspberryPI' / 'data')
_dataDir = str(_rootDir / 'data')


import ETL
import datetime
import dash
import dash_core_components as dcc
import dash_html_components as html
import plotly
from dash.dependencies import Input, Output

external_stylesheets = ['https://codepen.io/chriddyp/pen/bWLwgP.css']

app = dash.Dash(__name__, external_stylesheets=external_stylesheets)
app.layout = html.Div(
html.Div([
    html.H4('RaspberryPI Sensor Charts'),
    html.Div(id='live-update-text'),
    dcc.Graph(id='live-update-graph'),
    dcc.Interval(
        id='interval-component',
        interval=1*1000, # in milliseconds
        n_intervals=0
    )
])

)

 @app.callback(Output('live-update-text', 'children'),
          [Input('interval-component', 'n_intervals')])
def update_metrics(n):
     Temperature, Time = ETL.extractLastTemp(os.path.join(_dataDir, 
  'tempData.csv'))
style = {'padding': '2px', 'fontSize': '16px'}
return [
    html.Span('Temperature: {}'.format(Temperature), style=style),
    html.Span('Time: {}'.format(Time), style=style)
]


# Multiple components can update everytime interval gets fired.
@app.callback(Output('live-update-graph', 'figure'),
          [Input('interval-component', 'n_intervals')])
def update_graph_live(n):

     #Load Temp Data 
     tempDict = ETL.etlTransform(os.path.join(_dataDir, 
  'tempData.csv'))
    lightDict = ETL.etlTransform(os.path.join(_dataDir, 
  'lightData.csv'))
      currentDict = ETL.etlTransform(os.path.join(_dataDir, 
 'currentData.csv'))
# Create the graph with subplots
fig = plotly.tools.make_subplots(rows=3, cols=1, vertical_spacing=0.2, subplot_titles=("Temperature", "Light", "Current"))
fig['layout']['margin'] = {
    'l': 30, 'r': 10, 'b': 30, 't': 25
}
fig['layout']['legend'] = {'x': 0, 'y': 1, 'xanchor': 'left'}
fig['layout']['height'] = 900

fig.append_trace({
    'x': tempDict.keys(),
    'y': tempDict.values(),
    'name': 'Temp vs. Time',
    'mode': 'lines+markers',
    'type': 'scatter'
}, 1, 1)
fig.append_trace({
    'x': lightDict.keys(),
    'y': lightDict.values(),
    # 'text': data['time'],
    'name': 'Light vs. Time',
    'mode': 'markers',
    'type': 'scatter'
}, 2, 1)
fig.append_trace({
    'x': currentDict.keys(),
    'y': currentDict.values(),
    # 'text': data['time'],
    'name': 'Current vs. Time',
    'mode': 'markers',
    'type': 'scatter'
}, 3, 1)

return fig

def main(): app.run_server(debug = True)

if name == 'main': main() # app.run_server(debug=True)

  • same data in _dataDir folder on both RPI and Mac? – abolotnov Oct 9 at 5:27
  • Yes I dont believe its a pathing issue.....I print an os.listdir(_dataDir) to see if it can find the directory and print out its contents.....it does.... – Tuomas Talvitie Oct 9 at 15:24
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so I was able to fix the issue by increasing the update interval. I guess on raspberry Pi, the interval needs to be larger in order for the chart to update correctly. Weird, but it works.

Looks like its an ongoing issue with Dash.

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