Tuesday, June 4, 2013

pi2go Is working 100%

For those that may like an update on how well pi2go is working. Well the answer is quite well actually. For this reason I will walk you through its functionality and how it works. pi2go Is written in python 2.7 utilizing pyQt4 and pySerial for Raspberry Pi. It is being created as an easy UI for a vehicle computer. So far the only feature is reading engine information from the OBDII sensor via Bluetooth.

First off in Figure 1 below  displays the given start screen.

Figure 1
As stated in a previous post I would like to place a clock in the blank space on the right. Before I attempt that I need a little more info on QThreads. Pressing the "OBDII" tab will bring up the OBDII scanning feature displayed in Figure 2 below.
Figure 2
These are the current engine stats that are being read. Currently the values are updated every 1sec, I will be adding selector so this value can be changed to personal preference. Pressing the display "Start" button will initialize the scanning thread. (Thats right this python novice introduced multithreading.) This simply mean the background process is taking place outside the main program so it does not slow itself down.
obdThread = Thread(target=self.write_to_UI(obdValue), args = (self,obdValue)) 
obdEvent = Event()
obdThread.start()
Figure 3 and 4 below display the running program.
Figure 4

Figure 3  
Above Figure 3 displays information as it comes in, before it is updated on Figure 4.
def write_to_UI(self,values):
"""Updates the UI with new values"""
# receive [speed, rpm, intake, coolant, load]
self.ui.lcdNumber_speed.display(values[0])
self.ui.lcdNumber_rpm.display(values[1])
self.ui.lcdNumber_inTemp.display(values[2])
self.ui.lcdNumber_coolTemp.display(values[3])
self.ui.lcdNumber_load.display(values[4])
QtGui.QApplication.processEvents() #Writes all pending changes to QT
return
The guts behind the scanning thread is all in pySerial. The code below show how the scanner obtains values from the OBDII sensor. This example is the speed however the method is the same for all.

First a serial port is connected, "rfcomm0" at a baud rate of "38400".
self.serialIO = serial.Serial('/dev/rfcomm0', 38400, timeout=1)
Then using the serialport you send send a hexadecimal PID which can be found here. In this case we send "01", "0D" and want a return "\r". ("01" stands for the current value, "0D" is speed.)
self.serialIO.write("01 0D \r")
The above line will return a list of 1 string "['410D1D\r\r>']" not including quotes. The bold values are what is needed. They are a hexadecimal value so the code below first pulls the needed values by treating the string as a list. Then converts (Using the example) from a string, '1D', to hex value '0x1D' to an integer, base zero, 29 to a float 29.0 The final answer being in Kph
(I apologize for that long run on sentence I hope you were able to follow)
speed_list = self.serialIO.readline().split(' ')
speed_hex = speed_list[0][4:6]
speed_float = float(int("0x"+speed_hex, 0))
 
I then converted the value to Mph and returned it in a list with other values.
speed_float = speed_float*0.621371 #Comment out if you would rather have Kph
return speed_float
The last feature I added in this version is the ability to clear error codes. It is placed in the setting tab as depicted in Figure 5.
Figure 5
This tab will have more options evenly and will have feedback to the clearing function.

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There you have it the basic functionality of pi2go and how it works. Any feedback will be outstanding!
As always if you would like to follow/keep up on this blog or check out github. I have many new features to add.

**For those that care written in Python2.7 utilizing pyQt4 over pySerial. Issue tracker