RS232 serial commands

[Charles Linquis]

It depends a lot on whether or not your program is going to wait around for
the input, or if it needs to do something else while waiting. Or whether or not your input will come from a keyboard (time between characters) or all at once.

One way would be to -

 
LookForStart:
 
 
FoundStart = 0  
 
 
HSERIN 1000,NoData,[WAIT ("start")] : FoundStart=1
 
 
Return
 
 
 
 
 
NoData:
 
 
Return

FoundStart will = 1 if the "start" was received after waiting for 1 second.

[pxidr84]

It depends a lot on whether or not your program is going to wait around for
the input, or if it needs to do something else while waiting. Or whether or not your input will come from a keyboard (time between characters) or all at once.

One way would be to -

LookForStart:
 
 
FoundStart = 0  
 
 
HSERIN 1000,NoData,[WAIT ("start")] : FoundStart=1
 
 
Return
 
 
 
 
 
NoData:
 
 
Return

FoundStart will = 1 if the "start" was received after waiting for 1 second.

I use this :

DEFINE OSC 40      
DEFINE LCD_DREG PORTD
DEFINE LCD_EREG PORTB
DEFINE LCD_RSREG PORTB
DEFINE LCD_EBIT 6
DEFINE LCD_RSBIT 7
DEFINE ADC_BITS 10
DEFINE HSER_RCSTA 90h 
DEFINE HSER_TXSTA 20h 
DEFINE HSER_BAUD 9600
DEFINE HSER_SPBRG 64


char var WORD
foundstart var bit


pause 1000
HIGH PORTE.2
LCDOUT $fe,1
Hserout ["Program has started."] 
pause 1000


LookForStart:
  
FoundStart = 0  
  
HSERIN 5000,noData,[WAIT ("start")] : FoundStart=1
 
Return
 
  
nodata:
 
if FoundStart=1 then 
   HIGH PORTD.4
   Lcdout $fe,2,"Backlight ON."
ENDIF
 
Return

And it doesn't work, every 5 seconds I receive "Program has started".
Now I'm using Terminal v1.9b by Bray, it's far better because I can send a word at once. So no time between characters.

And yeah, my program have a lot things to do (interrupts, etc.) during this time. Here I'm using a very simple program to get started.

[mister_e]

try something like that

        DEFINE OSC 40      
        DEFINE HSER_RCSTA 90h 
        DEFINE HSER_TXSTA 20h 
        DEFINE HSER_BAUD 9600
        DEFINE HSER_SPBRG 64
    
Start:        
        Hserout ["Program has started.",13,10] 
        gosub LookForStart
        Goto Start

LookForStart:
        HSERIN 5000,noData,[WAIT ("start")] 
        hserout ["Got it! Backlight ON",13,10]
        Return
 
nodata:
        HSEROUT ["NOPE... Life's so cruel...",13,10]
        Return

[pxidr84]

try something like that

        DEFINE OSC 40      
        DEFINE HSER_RCSTA 90h 
        DEFINE HSER_TXSTA 20h 
        DEFINE HSER_BAUD 9600
        DEFINE HSER_SPBRG 64
    
Start:        
        Hserout ["Program has started.",13,10] 
        gosub LookForStart
        Goto Start

LookForStart:
        HSERIN 5000,noData,[WAIT ("start")] 
        hserout ["Got it! Backlight ON",13,10]
        Return
 
nodata:
        HSEROUT ["NOPE... Life's so cruel...",13,10]
        Return

Thanks!

HSERIN command remind me the BUTTON command (with the label).

So I use this :

DEFINE OSC 40      
DEFINE LCD_DREG PORTD
DEFINE LCD_EREG PORTB
DEFINE LCD_RSREG PORTB
DEFINE LCD_EBIT 6
DEFINE LCD_RSBIT 7
DEFINE ADC_BITS 10
DEFINE HSER_RCSTA 90h 
DEFINE HSER_TXSTA 20h 
DEFINE HSER_BAUD 9600
DEFINE HSER_SPBRG 64

Hserout ["Varidrive V2011.00 has started"] 
 
mainlp:        
      
LCDOUT $fe,2,"Main loop"
        
HSERIN ret,[WAIT ("blon")] 
       HIGH PORTD.4
ret:

HSERIN ret1,[WAIT ("bloff")] 
       LOW PORTD.4
ret1:

Goto mainlp

And it works flawlessly.

However, when I type "blonn" instead of "blon", the backlight is activated.
Same thing with "blofffff" instead off "bloff", the backlight is disabled.

So I need a stop bit or something like that?

[mister_e]

OK, so you need to check a couple of different Strings possibilities and act upon right?

Is this really need to be string? Did you built the "Transmitting unit" or it's just for learning purpose?

Most common and easiest way to implement such thing is to wait for a specific header and then use the next Byte for specific command.
ex:
Transmitter send: "NextCommandIs", 10
Receiver Wait for "NextCommandIs" and store 10 in a byte variable. Depending the value of that Byte Variable, it process various task.

So Easy as
Transmitter Side:
HSEROUT ["NextCommandIs", 10]

Receiver Side:
HSERIN [WAIT ("NextCommandIs"), ByteA]
SELECT CASE ByteA
'
'
'
'

Should you really need to wait for a specific String, then you'll need to build a string with each single character you receive parse them. Not hard, just a tad longer to implement.

[mister_e]

Also, depending of how you send the whole thing, you may also check for a "end" character. If the string is right but the next character/byte is false, you discard the result.

All the time, you want to implement a structured "serial data message" on both side.

[mister_e]

Here's some inspiration, not 100% efficient but easy to follow.

        DEFINE OSC 40      
        DEFINE HSER_RCSTA 90h 
        DEFINE HSER_TXSTA 20h 
        DEFINE HSER_BAUD 9600
        DEFINE HSER_SPBRG 64
        WaitFor     var byte [4]
        CounterA    VAR BYTE
        clear
        Hserout ["Varidrive V2011.00 has started",13,10] 
 
main:   
        GOSUB ClearArray     
        HSEROUT ["Main loop",13,10]   
        HSERIN  5000, main,[WAIT ("blo")]
        HSERIN 500, testit, [str waitFor\3]
testit:
        SELECT CASE WaitFor[0]
                CASE "n"
                        if WaitFor[1]=0 then
                                HIGH PORTD.4
                                HSEROUT ["ON",13,10]
                                else
                                    GOSUB FAIL
                                endif
                            
                CASE "f"
                        if WaitFor[1]="f" then
                                if WaitFor[2]=0 then  
                                        LOW PORTD.4
                                        HSEROUT ["OFF",13,10]
                                        else 
                                                GOSUB FAIL
                                        ENDIF
                                endif
                CASE ELSE
                        GOSUB FAIL
                END SELECT
           goto main
        
ClearArray:
        FOR CounterA = 0 TO 3
                WaitFor[CounterA]=0
                next
        RETURN 
        
FAIL:
        HSEROUT ["FAIL!",13,10]
        RETURN