B4R Question Error handling in b4R, how to catch?

[yaniv hanya]

I need to create a app that will read a info from eeprom in the start.

my problem is that in the first time (or after Reset), the eeprom is empty and return Error.
I understand there is no "try/catch" block in b4r. so in first time reading, the app crashes...

How can i solve the problem? i need to do something like-
Try to read username, if it is empty return false, so we will go to the user to get the username.

For now, empty return error… and app stops.

thanks

 

[RJB]

Does this help? https://www.b4x.com/android/forum/threads/writing-and-reading-from-the-eeprom.65711/#content

 

[yaniv hanya]

i"l try it. it looks like it should help...

 

[Erel]

There is no Try / Catch in Arduino.

You need to save a "magic" marking (2 bytes for example with specific value) that you can later check and see whether the EEPROM was already written.

 

[yaniv hanya]

so, i need to install a first app, that will insert the "magic marking", and then the main app that will get and check the userName?
since the "Regular" app should run again and again, in case of wifi disconnection. or electric stop and so on...

 

[candide]

no need a first app to initialize EEPROM
First, when user/password is written, the 2 first bytes aree Magic byte and length of data
After,you can read first 2 first bytes in eeprom , use/passwors if present if byte 0= Magic EEPROM in byte 0, and byte 1 = length of data
something like that:

Private const MAGIC_EEPROM As Byte = 213

Public Sub GetStoredDataLength As Byte
    Dim header() As Byte = eeprom.ReadBytes(0, 2)
'    Log("header lu=",header(0),"+",header(1))
    If header(0) = MAGIC_EEPROM Then
        Return header(1)
    End If
    Return 0
End Sub

Sub    GetStoredData As Byte
    Dim length As Byte = GetStoredDataLength    
'    Log("length wifi=",length)
    If length > 0 Then
        Dim ObjectsBuffer(18) As Object
        Dim Data() As Byte = eeprom.ReadBytes(2, length)
        Dim Objects() As Object = sr.ConvertBytesToArray(Data, ObjectsBuffer)
        If Objects.Length <> 0 Then
'          For Each o As Object In Objects
'            Log("obj_wifi",o)
'          Next
          For i = 0 To 17
          GStore1.Put(i,Objects(i))
          Next
          Return 1
        Else 
          Return 0
        End If    
    Else
        Return 0    
    End If          
End Sub

Public Sub SaveNetworkDetails(Data() As Byte)
    Log("Saving Network data")
    Log("data length: ", Data.Length)
'    Log("data to eeprom=",Data)
    eeprom.WriteBytes(Array As Byte(MAGIC_EEPROM, Data.Length), 0)
    eeprom.WriteBytes(Data, 2)
 '   ConnectToNetwork
End Sub

 

[yaniv hanya]

Thank you.

if the eeprom didn't format or written, will line 4 in the code will not return error?

 

[candide]

this code was used on esp8266 /esp32 to avoid issue in case of no data.

to clear data, i just erase bytes 0 and 1 in eeprom

 

[yaniv hanya]

thank you very much. i"l try in my side.

 

[Erel]

if the eeprom didn't format or written, will line 4 in the code will not return error?

No. The EEPROM doesn't need to be formatted and it always holds data. Don't assume anything about the data that is prestored.