Help Read GPIO pin in Python

booman171

Hello everyone. I have been attempting to read the analog signal from the GPIO pin of the MetamotionR board. I am using the pymetawear library on a raspberry pi.

This is the sesnor I am attempting to read: https://www.sparkfun.com/products/12650?_ga=2.112552772.1984315370.1584943763-165751714.1579836749

Reading the sesnor from the GPIO pin with the MetaWear android app does work. However when I try to test it in python I am stuck.

I have been modifying the gpio.py script in the pymetawear modules folder. Here is my code:

https://github.com/booman171/gpio/blob/master/gpio.py

Note, this file is a copy of the the gpio.py file from the modules folder within a clone of the pymetawear library, in which I am editing. I have been playing around with the code around line 100 but nothing seems to work.

There error message is as follows:

Traceback (most recent call last):
  File "gpio.py", line 217, in <module>
    gp.notifications(handle_gpio_notification)
  File "gpio.py", line 197, in notifications
    super(GpioModule, self).notifications(data_handler(callback))
  File "/usr/local/lib/python3.7/dist-packages/pymetawear/modules/base.py", line 135, in notifications
    data_signal = self.data_signal
  File "gpio.py", line 100, in data_signal
    return libmetawear.mbl_mw_gpio_get_pin_monitor_data_signal(self.board, '0')
ctypes.ArgumentError: argument 2: <class 'TypeError'>: wrong type

Any help is welcome.

Laura

Please check this out for help: https://github.com/mbientlab/MetaWear-SDK-Cpp/blob/master/test/test_gpio.py

booman171

I have been looking through that example, thank you. I managed to get passed my initial issue, but still can't access the signal.

This is my code:

# usage: python stream_acc.py [mac1] [mac2] ... [mac(n)]
from __future__ import print_function
from mbientlab.metawear import MetaWear, libmetawear, parse_value
from mbientlab.metawear.cbindings import *
from time import sleep
from threading import Event
from ctypes import byref, create_string_buffer
import platform
import sys

if sys.version_info[0] == 2:
    range = xrange

class State:
    def __init__(self, device):
        self.device = device
        self.samples = 0
        self.callback = FnVoid_VoidP_DataP(self.data_handler)

    def data_handler(self, ctx, data):
        print("%s -> %s" % (self.device.address, parse_value(data)))
        self.samples+= 1

states = []
d = MetaWear("CC:3E:36:3A:4B:50")
d.connect()
print("Connected to " + d.address)
states.append(State(d))

for s in states:
    print("Configuring device")
    libmetawear.mbl_mw_settings_set_connection_parameters(s.device.board, 7.5, 7.5, 0, 6000)
    sleep(1.5)
    an_signal = libmetawear.mbl_mw_gpio_get_analog_input_data_signal(s.device.board, 2, GpioAnalogReadMode.ADC)
    libmetawear.mbl_mw_datasignal_subscribe(an_signal, None, s.callback)
    libmetawear.mbl_mw_gpio_start_pin_monitoring(s.device.board, 2)
    libmetawear.mbl_mw_datasignal_read(an_signal)

sleep(15.0)

for s in states:
    libmetawear.mbl_mw_gpio_stop_pin_monitoring(s.device.board, 2)
    an_signal = libmetawear.mbl_mw_gpio_get_analog_input_data_signal(s.device.board, 2, GpioAnalogReadMode.ADC)
    libmetawear.mbl_mw_datasignal_unsubscribe(an_signal)
    libmetawear.mbl_mw_debug_disconnect(s.device.board)

print("Total Samples Received")
for s in states:
    print("%s -> %d" % (s.device.address, s.samples))

The output is:

Connected
Services disconvered
Characteristics discovered
Descriptors found
Connected to CC:3E:36:3A:4B:50
Configuring device
CC:3E:36:3A:4B:50 -> 401
Total Samples Received
CC:3E:36:3A:4B:50 -> 1

There should be some output here. Any thoughts?

Laura

This looks all correct. You only read the signal once so you got one sample. Please read our tutorials, some signal need timers to be read more than once:
https://mbientlab.com/tutorials/CPPDevelopment.html#reading