Returning a byte value of 0 when reading from USART

[Jeff Weinmann]

Hello again,

I'm in the process of converting code from MikroBasic to GCB and I'm getting a strange value back from USART2.

Basically the code in MB worked by checking if there was data ready on either UART1 or UART2, then reading it:

'MikroBasic Code...
        if UART1_Data_Ready() = 1 then
           receive = UART1_Read()
           Select Case receive
                  Case "0"
                       OpMode = 0 'Initial Operation
                       AutoPPS = 0

                  Case "1"
                       'Cant enter diagnostic until we have a fix
                       If GPSMode = 1 then
                         OpMode = 1 'GPS Diagnostic
                         UART1_Write_Text("GPS Active")'Send back acknowledge to Interface
                         UART1_Write(10)
               End Select
           end if

I'm trying to do something similar, in GCB. I'm only looking for 1 return byte from the comport device, a number from 0 to 5. Here's my implementation:

Do Forever
'Pole MCU for Data
      'If there is no new data, HSerReceive will return default value of 255
      comport = 2
      HSerReceive2(TempByte)
      'Do nothing if it is default
      If TempByte <> 255 Then
        if TempByte = 0 then
              HSerPrint "TempByte is 0", 2
              HSerSend 13,2
              HSerSend 10,2
        else
              HSerPrint "TempByte is NOT 0, but I cannot get any other value so this never gets hit.", 2
              HSerSend 13,2
              HSerSend 10,2
        end if

      End If
      comport = 1

      Wait 100 ms

    Loop

I'm using the USART2 on a PIC18F16Q40. I set up the USARTS (and I2c) with PPS:

#startup InitPPS, 85
    #define PPSToolPart 18f16q40

    Sub InitPPS

            'Module: I2C1
            RB6PPS = 0x0021    'SCL1 > RB6
            I2C1SCLPPS = 0x000E    'RB6 > SCL1 (bi-directional)
            RB4PPS = 0x0022    'SDA1 > RB4
            I2C1SDAPPS = 0x000C    'RB4 > SDA1 (bi-directional)

            'Module: UART pin directions
            Dir PORTC.6 Out    ' Make TX1 pin an output
            Dir PORTC.7 In    ' Make RX1 pin an input
            Dir PORTC.0 Out    ' Make TX2 pin an output
            Dir PORTC.1 In    ' Make RX2 pin an input
            'Module: UART1
            RC6PPS = 0x0010    'TX1 > RC6
            U1RXPPS = 0x0017    'RC7 > RX1
            'Module: UART2
            RC0PPS = 0x0013    'TX2 > RC0
            U2RXPPS = 0x0011    'RC1 > RX2
    End Sub

    'USART settings for UART1 and UART2
#define USART_BAUD_RATE 9600
#define USART_BLOCKING
#define USART_TX_BLOCKING

#define USART2_BAUD_RATE 9600
'#define USART2_BLOCKING
'#define USART2_TX_BLOCKING
'#define USART_DELAY OFF

USART2 is non blocking so I'm trying to read as it comes in. I don't have more than 1 byte that I'm looking for so a ring buffer i think is overkill for this.

I did try

On Interrupt UsartRX2Ready Call getdata

sub getdata
'Receive code....
....
....
end sub

and got :
Error: Invalid interrupt event: USARTRX2READY

I think if I can add the interrupt on USART2 and get it working i might be further along.

What is strange is that every time I send the 1 byte flag from the com device, my polling and my return messages work, I can never get anything but a '0' byte value

May I get help with proper syntax to setup an interrupt on USART2? thanks Any thoughts on the 0 value byte returned?

Jeff

[mmotte]

Jeff ,
I am not sure what you are doing with the gps but I did some work a while back.
https://sourceforge.net/p/gcbasic/discussion/629990/thread/0e660522/

.......................................

     comport = 2
      HSerReceive2(TempByte)
      'Do nothing if it is default

to make this code more efficient, instead of checking for the default value, check directly for data available.
Just above this code

If  USART2HasData then
     comport = 2
      HSerReceive2(TempByte)

      ...... rest of you code 
  endif    

GL
Mike

USART2HasData is in the GCB usart.h library file . The usart only has one byte data buffer. If you need more then use a buffer.