B4R Question Guru Mediation Error: Core 0 panic'ed (Load access fault). Exception ws unhandled

daveinhull · Nov 26, 2023

Hi,

Now that I've got the ESP32 GC9A01A code working in the Arduino, I'm trying to move it into B4R, so trying to keep it as same as possible, espeially the sematics/strucutre before looking to alter it.

I'm getting the above error when calling a routine [edit: should have mentioned that it gets about half way through processing the initial command and repeatedly fails at the same point, but can't see anything unusual at that point]

B4X:

SendCommand(Cmd,Convertor.subString(InitCmd,CmdPointer),Bit.And(InitCmd (CmdPointer),0x7f))

The routine defintion is:

B4X:

Private Sub SendCommand (CommandByte As Byte, DataBytes() As Byte, NumberDataBytes As Byte)

The InitCmd array is (completely as is in the C code version):

B4X:

    InitCmd = Array As Byte (GC9A01A_INREGEN2, 0, _
    0xEB, 1, 0x14, _
    GC9A01A_INREGEN1, 0, _
    GC9A01A_INREGEN2, 0, _
    0xEB, 1, 0x14, _
    0x84, 1, 0x40, _
    0x85, 1, 0xFF, _
    0x86, 1, 0xFF, _
    0x87, 1, 0xFF, _
    0x88, 1, 0x0A, _
    0x89, 1, 0x21, _
    0x8A, 1, 0x00, _
    0x8B, 1, 0x80, _
    0x8C, 1, 0x01, _
    0x8D, 1, 0x01, _
    0x8E, 1, 0xFF, _
    0x8F, 1, 0xFF, _
    0xB6, 2, 0x00, 0x00, _
    GC9A01A_MADCTL, 1, MADCTL_MXorBGR, _
    GC9A01A_PIXFMT, 1, 0x05, _
    0x90, 4, 0x08, 0x08, 0x08, 0x08, _
    0xBD, 1, 0x06, _
    0xBC, 1, 0x00, _
    0xFF, 3, 0x60, 0x01, 0x04, _
    GC9A01A1_VREG1A, 1, 0x13, _
    GC9A01A1_VREG1B, 1, 0x13, _
    GC9A01A1_VREG2A, 1, 0x22, _
    0xBE, 1, 0x11, _
    ILI9341_GMCTRN1, 2, 0x10, 0x0E, _
    0xDF, 3, 0x21, 0x0c, 0x02, _
    GC9A01A_GAMMA1, 6, 0x45, 0x09, 0x08, 0x08, 0x26, 0x2A, _
    GC9A01A_GAMMA2, 6, 0x43, 0x70, 0x72, 0x36, 0x37, 0x6F, _
    GC9A01A_GAMMA3, 6, 0x45, 0x09, 0x08, 0x08, 0x26, 0x2A, _
    GC9A01A_GAMMA4, 6, 0x43, 0x70, 0x72, 0x36, 0x37, 0x6F, _
    0xED, 2, 0x1B, 0x0B, _
    0xAE, 1, 0x77, _
    0xCD, 1, 0x63, _
    0x70, 9, 0x07, 0x07, 0x04, 0x0E, 0x0F, 0x09, 0x07, 0x08, 0x03, _
    ILI9341_FRAMERATE, 1, 0x34, _
    0x62, 12, 0x18, 0x0D, 0x71, 0xED, 0x70, 0x70, 0x18, 0x0F, 0x71, 0xEF, 0x70, 0x70, _
    0x63, 12, 0x18, 0x11, 0x71, 0xF1, 0x70, 0x70, 0x18, 0x13, 0x71, 0xF3, 0x70, 0x70, _
    0x64, 7, 0x28, 0x29, 0xF1, 0x01, 0xF1, 0x00, 0x07, _
    0x66, 10, 0x3C, 0x00, 0xCD, 0x67, 0x45, 0x45, 0x10, 0x00, 0x00, 0x00, _
    0x67, 10, 0x00, 0x3C, 0x00, 0x00, 0x00, 0x01, 0x54, 0x10, 0x32, 0x98, _
    0x74, 7, 0x10, 0x85, 0x80, 0x00, 0x00, 0x4E, 0x00, _
    0x98, 2, 0x3e, 0x07, _
    GC9A01A_TEON, 0, _
    GC9A01A_INVON, 0, _
    GC9A01A_SLPOUT, 0x80, _
    GC9A01A_DISPON, 0x80, _
    0x00) ' End of list

Anyone any thoughts please - is it a problem with the ESP?
Thanks
Dave

daveinhull · Nov 26, 2023

Some info, according to the ESP32-C3 website covering fatal errors, this error is described as:

Instruction Access Fault, Load Access Fault, Store Access Fault

This CPU exception happens when application attempts to execute, read from or write to an invalid memory location. The address which was written/read is found in MTVAL register in the register dump. If this address is zero, it usually means that application attempted to dereference a NULL pointer. If this address is close to zero, it usually means that application attempted to access member of a structure, but the pointer to the structure was NULL. If this address is something else (garbage value, not in 0x3fxxxxxx - 0x6xxxxxxx range), it likely means that the pointer used to access the data was either not initialized or was corrupted.

My registers were:
MSTATUS : 0x00001881 MTVEC : 0x40380001 MCAUSE : 0x00000005 MTVAL : 0x0000001d
so it looks like it relates to

....If this address is close to zero, it usually means that application attempted to access member of a structure.....

But looking at the vaues and pointers just before it crashes, there are:
Command = 90; Pointer = 59; No = 4

Not sure I'm good enough to work this one out, any ideas anyone?
Thanks

daveinhull · Nov 26, 2023

Just some further info, the routine loos like this:

B4X:

Private Sub SendCommand (CommandByte As Byte, DataBytes() As Byte, NumberDataBytes As Byte)
    Log ("In send command")
    CSpin.DigitalWrite(False)
    DCpin.DigitalWrite(False)
    Log("Pins set low")
    HSPI.transfer(Array As Byte(CommandByte),1)
    Log ("Transfered command")
    If NumberDataBytes <> 0 Then
        DCpin.DigitalWrite(True)
        HSPI.transfer(DataBytes,NumberDataBytes)
        Log ("Transfered Data")
    End If
    CSpin.DigitalWrite(True)
    Log ("Pins Low")
End Sub

I get the part of the log message "In send comm" and then it crashes

B4R Question Guru Mediation Error: Core 0 panic'ed (Load access fault). Exception ws unhandled

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