Wipy 2.0 and save data on my pc, not in flash memory

[robert-hh]

@vflorio94 A python script is a text file, just with the extension .py. You can start that from sd card with two methods:
a) change the active directory to the card before import
mount the card
os.chdir("/sd")
import file
b) change the system path.
If you
import sys
print(sys.path)
you get something like ['', '/flash', '/flash/lib'], which is the list of places where the python scripts are looked for. '' is the actual directory. You can add "/sd" to that path with:
sys.path.append("/sd")
you can also directly set sys.path to the list of places.

[VFlorio94]

@robert-hh I try to update my main.py and my lib.py on sd card but I can't understand where i have to put the command that you wrote.

[robert-hh]

@vflorio94 You have to put that in boot.py or main.py in flash, because that is executed in first place.

[VFlorio94]

@robert-hh thank you, I do it.
another question, if I read data from a file.txt and I want to reuse this data, what is the way to import and/or assign them to a local variable?
thank you

[robert-hh]

@vflorio94 To read the data from a file, you could read it all in once, assumign f is the opened file, with:

text = f.readlines()

then text is a list of strings. That however will use a lot for RAM. You can also read line by line with:

for line in f:
# line is one line to be processed

[VFlorio94]

@robert-hh YEs, but i have a file.txt with this content

[169.5, 169.5, 169.5, 169.5, 169.5, 169.5, 169.5, 169.5, 169.5, 169.5, 169.5, 169.5, 169.5, 169.5, 169.5, 169.5, 169.5, 169.5, 169.5, 169.5, 169.5, 169.5, 169.5, 169.5, 169.5, 169.5, 169.5, 169.5]  [0.1875, 0.1875, 0.1875, 0.1875, 0.1875, 0.1875, 0.1875, 0.1875, 0.1875, 0.1875, 0.1875, 0.1875, 0.1875, 0.1875, 0.1875, 0.1875, 0.1875, 0.1875, 0.1875, 0.1875, 0.1875, 0.1875, 0.1875, 0.1875, 0.1875, 0.1875, 0.125, 0.1875]       [-177.5625, -177.5625, -177.5625, -177.5625, -177.5625, -177.5625, -177.5625, -177.5625, -177.5625, -177.5625, -177.5625, -177.5625, -177.5625, -177.5625, -177.5625, -177.5625, -177.5625, -177.5625, -177.5625, -177.5625, -177.5625, -177.5625, -177.5625, -177.5625, -177.5625, -177.5625, -177.625, -177.5625] 

I want to iterate data by data in this file and compare them with other value trough control 'if'.
for example I want to use data in the first square brackets and step by step compare them with other numeric value, do you know a way to do this?
I am not able to convert them in numeric value and compare them one by one, I know that i have to use a 'for' to pass all the value but I am not succeded.

[robert-hh]

@vflorio94 Can you create the file in a different format, like having one line for each set of data in brackets?

[robert-hh]

@vflorio94 You can do something like:

f = open("file.txt", "r")
line = f.read()
f.close()
# now you have the full test in one string
list = line.split("[")
# now you have a list of three strings, and an empty one
# remove the empty ones
for index, item in enumerate(list):
    if len(item) == 0:
        del list[index]
# convert to numeric value
for index, item in enumerate(list):
    item = item.strip("] ").split(",")
    # now item is a list of numeric strings
    for i, el in enumerate(item):
        item[i] = float(el)
    list[index] = item
    # now list is a list of lists with numeric values
    # indexing by list[i][j]

[VFlorio94]

@robert-hh yes, i'll create a file in which I put one set of data in brackets in a line, then there is a way to extract a single data and do a control on it and then pass to the data in the next position?

[robert-hh]

@vflorio94 In my previous post I showed a code snippet, if all data is in one line. If each bracket is in a separate line, then the code snippet is much simpler.

f = open("file1.txt", "r")
list = f.readlines()
f.close()
# now you have a list of one string per line
for index, item in enumerate(list):
    item = item.strip("[]\n ").split(",")
    # now item is a list of numeric strings
    for i, el in enumerate(item):
        item[i] = float(el)
    list[index] = item
    # now list is a list of lists wirth numeric values

[VFlorio94]

@robert-hh Thank you, I didn't see your comment before. At the end I am succeded in a similar way, now i'll try also yours
thank you very much

[robert-hh]

@vflorio94 Shortened version, not easy to read:

with open("file.txt", "r") as f:
    list = f.readlines()
    # now you have a list of one string per line
    for index, item in enumerate(list):
        list[index] = [float(el) for el in item.strip("[]\n ").split(",")]
        # now list is a list of lists with numeric values
        # accessible with list[i][j]

[VFlorio94]

@robert-hh the data now are like this

348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000 ,348.750000
<class 'str'>

so i do:

f= open("/sd/dat.txt", "r").read()
f.close()
f1 = f.split(',')
g = []
for i in range(1, len(f1)):
    h = float(f1[i])
    g.append(h)

[robert-hh]

Usign a generator instead of the loop, it can be written e.g. like:

with open("data.txt", "r") as f:
    line = f.read()
    # now you have a list of one string per line
    g = [float(el) for el in line.strip().split(",")]

or even shorter as

with open("data.txt", "r") as f:
    g = [float(el) for el in  f.read().strip().split(",")]

The last expression in the bracket is a little bit cryptic, to be read from left to right as:

• read the line
• strip of leading and trailing whitespace
• split it at , into a list of numeric strings, which is the fed into the generator expression.

[VFlorio94]

@robert-hh thank you, all the code that you wrote run correctly. I understand also your explanation.
thank you a lot !!

[robert-hh]

@vflorio94 A simpler way to store and load is using the ujson module. So if you have a list of values like g, write it with:

import ujson
with open("data.txt", "w") as f:
    ujson.dump(g, f)

and read it back with:

with open("data.txt", "r") as f:
    g = ujson.load(f)

In the micropython.lib, there is also the a pickle module.https://github.com/micropython/micropython-lib/tree/master/pickle

[VFlorio94]

@robert-hh Thank you.
unfortunately I have a new problem with wipy and I2C .

In the library for I2C if i set baudrate to 100k it doesn't work.
but in the data sheet of IMU it is written that it can work with a baudrate with a maximum of 400k.
the error is this one:

  File "/flash/lib_imu.py", line 382, in get_euler
  File "/flash/lib_imu.py", line 318, in read_vector
OSError: I2C bus error

I don't know how i can solve this bus error. Do you have an idea about this topic?

[robert-hh]

@vflorio94 Does it work at lower baud rates? if yes, then maybe the pull-up resistors are missing. The SDA and SCL lines must have a pull-up resistor in the range of 4.7 kOhm. Sometimes they are built on the board, sometimes not. The ESP32 has internal pull-up resistors at about 30 kOhm, which is good for lower baud rates.

[VFlorio94]

@robert-hh It works at lower baudrate like 10K, 15K but for value higher then 20K it doesn't work.

[robert-hh]

@vflorio94 Which BN055 module are you using, and how long are the connecting wires?