usart5 not supported on 18f27Q83

[Sommi]

Hi!

I tried to get usart 5 running on 18f27Q83 but was informed it is not supported yet. Any workarounds?

Kind regards Sommi

[Sommi]

Instead of using HRSOUT5 should i just declare putchar for usart5 and then send my message?


' Send a character to the USART transmitter
Proc PutChar()
    If PIR1.4 = 0 Then PutChar      ' Wait for transmit register empty
    TXREG = B1                      ' Send character to transmit register
EndProc

[Sommi]

Receive will be done in ISR anyway

[trastikata]

Any workarounds?

I generally prefer to have full control over USART peripheral therefore I set the registers manually, then read and write to the USART using the the buffer registers.

Besides it is easy to set a hardware interrupt for the USART RX which allows the whole process of receiving longer data strings to share CPU cycles with other routines and not get stuck in a loop.

My point, use the USART registers to set-up, read and write.

[Sommi]

Thanks trastikata

the only thing I use is hrsout, all the other stuff I do manually.

Would this be the way to send single characters?

Proc PutChar5(tx_char)
    while u5errirbits_txmtif = 0 : wend     ' Wait for transmit register empty
    u5txb = tx_char                      ' Send character to transmit register
EndProc

how would a procedure look to send a string like hrsout?

[trastikata]

how would a procedure look to send a string like hrsout?

Hi Sommi,

This is a basic example what it could look like, however I did not have time to test it in the simulation and I omitted the USART set-up. There should be working examples in the boards too, I think Les posted TX-RX example couple of times.

Code Select Expand

Device 18F25K20
Declare Xtal = 4

Symbol TXIF = PIR1.4
Symbol TXIE = PIE1.4
Symbol TXEN = TXSTA.5

Dim TxString As String * 64 'TX string
Dim pTxBusy As Bit          'TX busy flag
Dim bTxLength As Byte       'String length to send
Dim bTxCounter As Byte      'TX counter

On_Hardware_Interrupt GoTo Isr
GoTo Main

Isr:
    Context Save
        If TXIF = 1 And TXEN = 1 Then                   'Is it a valid TX Interrupt?
            If bTxCounter = (Bound(TxString) + 1) Then  'Reached end of TX string?
                TXIE = 0 : TXEN = 0                     'Yes, then stop and clear flags
                pTxBusy = 0
            Else                                        'No, then continue       
                If bTxLength = 0 Then                   'Is it actual string length to send
                    If TxString[bTxCounter] <> 0 Then   'Yes, then is it a null character?
                        TXREG = TxString[bTxCounter]    'No, then send it.
                        Inc bTxCounter                  'Increment TX counter
                    Else                                'Yes, then stop and clear flags
                        TXIE = 0 : TXEN = 0               
                        pTxBusy = 0
                    EndIf
                Else                                    'Then we send predetermined number of characters
                    If bTxCounter = bTxLength Then      'Did we send the predetermined number of characters?
                        TXIE = 0 : TXEN = 0             'Yes, then stop and clear flags 
                        pTxBusy = 0
                    Else
                        TXREG = TxString[bTxCounter]    'No, then send it.
                        Inc bTxCounter                  'Increment TX counter
                    EndIf
                EndIf
            EndIf
        EndIf   
    Context Restore

Main:
    If pTxBusy = 0 Then TxUsart("Test",0)
    End

'TxString  = String to send
'bTxLength = if <> 0 then number of characters to send
'            else send actual string length
Proc TxUsart(TxString As TxString, bTxLength As bTxLength)
    If bTxLength = 0 And TxString[0] <> 0 Or bTxLength > 0 Then 'Is there something to send?
        TXREG = TxString[0]                                     'Load first string character to TX buffer
        bTxCounter = 1                                          'Set TX counter
        pTxBusy = 1                                             'Set Tx busy flag
        TXEN = 1 : TXIE = 1                                     'Enable USART TX and TX Interrupt
    Else
        Return                                                  'Do nothing 
    EndIf
EndProc