B4R Tutorial SevSeg with inline C

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Johan Schoeman

Expert
Licensed User
This B4R project uses the SevSeg library via inline C to display characters on a 4 digit x 7 segment LED display (I am using a SMA420364L) - hard wired.

The inline C code via the SevSeg library does all the heavy lifting to display the chars on the 4 digit display. It can be used for common Anode and common Cathode displays as well as 1 to 4 digit displays. I have only tested in on a common Cathode display with 4 digits. The is an abundance of comments in the B4R code that explains setting the mode, number of digits, pins that will be used (see below wiring diagram), position of where the decimal point should be displayed, and brightness of the display (brightness from 0 to 100)

The attached B4R project simulates a clock. It displays the Hours:Minutes, then the Minutes:Seconds, and then just "HALO" and then cycles through the same sequence again.

Extract SevSeg.zip and copy the folder (with the .h and .cpp files) to your arduino libs folder.

Edit: Have posted a wrapper for SevSeg here

SevSegInline_bb.png


Sample Code:

B4X:
#Region Project Attributes
    #AutoFlushLogs: True
    #CheckArrayBounds: True
    #StackBufferSize: 300
#End Region

Sub Process_Globals
    'These global variables will be declared once when the application starts.
    'Public variables can be accessed from all modules.
    Public Serial1 As Serial
   
'    Dim bc As ByteConverter
   
    Dim mode_in As Boolean = False                    'common cathode (set to True for display with common Anode)    
    Dim numOfDigits As Byte = 4                       'Using a 4 digit x 7 segment LED display
    Dim digit1 As Byte = 13                           'Most significant digit i.e most left - pin 13
    Dim digit2 As Byte = 12                           '2nd digit from left - pin 12
    Dim digit3 As Byte = 11                           '3rd digit from left - pin 11
    Dim digit4 As Byte = 10                           'Least significant digit i.e most right - pin 10
    Dim segmentDP As Byte = 9                         'digital point - pin 9
    Dim segment1 As Byte = 2                          'Segment A - pin 2
    Dim segment2 As Byte = 3                          'Segment B - pin 3
    Dim segment3 As Byte = 4                          'Segment C - pin 4
    Dim segment4 As Byte = 5                          'Segment D - pin 5
    Dim segment5 As Byte = 6                          'Segment E - pin 6
    Dim segment6 As Byte = 7                          'Segment F - pin 7
    Dim segment7 As Byte = 8                          'Segment G - pin 8
    Dim brightness As Byte = 100                      'Set the brightness of the LED display between 0 and 100
   
    Dim min1, min10, hr1, hr10, sec10, sec1 As Byte   'keeping track of out clock thta we are setting up in AppStart
    Dim decimalposition As Byte = 2                   'set the decimal position to 2 (the 2nd DP from the left)
    Dim prevtime, currenttime As ULong
   
    Dim dat1() As Byte = "HALO"                       'set dat1 to "abcd" - we will pass it to the dsipaly in the timer
   
    Dim cnt As UInt = 0                               'a counter to decide what to display
                                                      'display will chnage between showing hour and minutes, minutes and seconds, "abcd", and then repeating this sequence of display
    Dim t As Timer                                    'We need a timer
   
End Sub

Private Sub AppStart
    Serial1.Initialize(115200)
    Log("AppStart")
    t.Initialize("t_tick", 20)                        'initialize the timer - tick every 20ms
    prevtime = Millis                                 'get the millis since MCU started
   
    hr10 = 1                                          'Set the hours, minuntes, and seconds here that you want to start the clock with
    hr1 = 9
    min10 = 2
    min1 = 2
    sec10 = 0
    sec1 = 0
   
    RunNative("begin", Null)                          'call Begin in SevSeg
    Delay(1)
    RunNative("SetBrightness", Null)                  'set the brightness of the LED's
    Delay(1)
    t.Enabled = True                                  'Enable the timer
   
End Sub

Sub t_tick
   
    cnt = cnt + 1                                     'increment the counter
   
    currenttime = Millis                              'get the current Millis
    If (currenttime - prevtime) > 1000 Then           'has 1 second gone by since previous "get Millis"?
        prevtime = currenttime                        'if so, then store current time to previous time
        sec1 = sec1 + 1                               'increment seconds 1's
        If sec1 > 9 Then
            sec1 = 0
            sec10 = sec10 + 1                         'increment seconds 10's
            If sec10 > 5 Then                         '.....sure you will follow the rest of the logic
                sec10 = 0
                min1 = min1 + 1
                If min1 > 9 Then
                    min1 = 0
                    min10 = min10 + 1
                    If min10 > 5 Then
                        min10 = 0
                        hr1 = hr1 + 1
                        If hr1 > 9 Then
                            hr1 = 0
                            hr10 = hr10 + 1
                        End If
                    End If
                End If
            End If
        End If
    End If
   
    If hr10 = 2 Then                             'check for midnight and if so set hr10 and hr1 to 0
        If hr1 = 4 Then
            hr10 = 0
            hr1 = 0
        End If
    End If
   
    If cnt < 500 Then                                                            'if counter is less than 500 then display HH.MM
        decimalposition = 2
        Dim c As String = JoinStrings(Array As String(hr10, hr1, min10, min1))   'build the string
        Dim b() As Byte = c                                                      'convert the string to a byte array
        RunNative("DisplayString", b)                                            'call DisplayString in SevSeg and pass it the byte array
    else if cnt < 1000 Then                                                      'if counter is > 500 and less than 1000 then display MM.SS
        decimalposition = 2
        Dim c As String = JoinStrings(Array As String(min10, min1, sec10, sec1))  
        Dim b() As Byte = c
        RunNative("DisplayString", b)
    else if cnt < 1500 Then                                                      'if counter >= 1000 but < 1500 then display dat1 = abcd
        decimalposition = 0
        RunNative("DisplayString", dat1)
    Else
        cnt = 0  
    End If
   
End Sub

#if C

#include <SevSeg.h>

SevSeg sevseg;                                                                 //We are using the SevSeg library

void begin(B4R::Object* o) {                                                   //begin - called from B4R code to set up mode(common cathode/anode), number of digits on the display, pins that are used, and where the digital point should be displayed
   sevseg.Begin(b4r_main::_mode_in, b4r_main::_numofdigits, b4r_main::_digit1, b4r_main::_digit2, b4r_main::_digit3, b4r_main::_digit4, b4r_main::_segment1, b4r_main::_segment2, b4r_main::_segment3, b4r_main::_segment4, b4r_main::_segment5, b4r_main::_segment6, b4r_main::_segment7, b4r_main::_segmentdp);
}

void SetBrightness(B4R::Object* o) {                                           //set the brightness of the LED's on the 7 segment display
   sevseg.SetBrightness(b4r_main::_brightness);
}

void DisplayString(B4R::Object* o) {                                          //what do display - passed in from the B4R code and received here as a B4R Object
   B4R::Array* conversion = (B4R::Array*)B4R::Object::toPointer(o);
   char* toDisplay = (char*)conversion->data;                                
   sevseg.DisplayString(toDisplay, b4r_main::_decimalposition);
}


#End If
20190621_201236.jpg
 

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