StackOverflowException gpio callback lgGpioSetAlertsFunc error

[Eugene_Dakin]

Hello,

I am writing an lgpio library glpio-GPIO that uses a callback function called lgGpioSetAlertsFun (lgGpio.

The exact error is ‘An exception of class StackOverflowException was not handled. The application must shut down.’

Setting up the GPIO is with the following code in the Opening event:

Sub Opening() Handles Opening
#Pragma X86CallingConvention StdCall
#Pragma StackOverflowChecking False
#Pragma DisableBackgroundTasks
//Initialize the Raspberry Pi lgpio
MyChipHandle = lgGpiochipOpen(0) //dev/gpiochip0

Pin27Echo = 27 //Echo input #27

Var RetVal As Integer
RetVal = lgGpioClaimAlert(MyChipHandle, 0, LG_BOTH_EDGES, Pin27Echo, -1)
System.DebugLog “1, Retval:” + RetVal.ToString

RetVal = lgGpioSetAlertsFunc(MyChipHandle, Pin27Echo, AddressOf cbf, Nil)
System.DebugLog “2, Retval:” + RetVal.ToString
End Sub

The code runs, and when I raise the voltage to 3.3v, the cbf function is to fire, and then the StackOverslowException error occurs.

Public Sub cbf(e as Ptr, lgGpioAlert_p as ptr, userdata as String)
//This is a callback which must be in a module
Window1.ListBox1.AddRow(“Fired”)
//Var i As Integer
System.DebugLog “3”
End Sub

Is there any helpful hints to stop the StackOverflowException error?

Thanks a bunch

[Björn_Eiríksson]

If the callback originates from gpio interupt then you almost certainly cannot talk to ListBox in the callback. (Or any Xojo object or string)

[Eugene_Dakin]

Thank you Bjorn.

[Christian_Schmitz]

Check out DeclareCallbackMBS class in MBS Xojo Plugins, which provides thread safe callbacks.