Can PBP & 16f88 really do 9600,8,E,1

[retepsnikrep]

I'm making good progress with my code thanks.

I have a couple of questions about Arrays and the addressing of them with pbp.

If I define an array thus.

BCMDATA VAR BYTE[11]		'Define BCMDATA as a byte array (11 Bytes)

I get an array 11 bytes long and the address of the first byte is

BCMDATA[0] and the last BCMDATA[10] ?

Is that correct.

Now onto for next loops.

CalcSum:					'Calculate Packet CheckSum Routine
	
	For Count1 = 0 to 10			'For Count1 = 0 to 10 (Start 11 byte loop)
	CheckSum = CheckSum + BCMDATA[Count1]	'Add Bytes
	Next Count1				'Repeat until 11 bytes added
	CheckSum = NOT CheckSum			'Not CheckSum
	CheckSum = CheckSum + 1			'Add 1 to CheckSum
	BCMDATA[10] = CheckSum AND $7F 		'AND result
	Return					'Return

In this code how many times does it complete?
And on the first pass through the loop Count1 =0 does it not?
And on the last pass through the loop Count1 = 9 or 10

So if count1 = 9 it goes through the loop, if it = 10 it jumps over it?

Just checking my understanding. Thanks

[mackrackit]

Sounds like you are getting it.

I would add
Count1 = 0
just before the for/next loop.

[retepsnikrep]

I would add
Count1 = 0
just before the for/next loop.

Why? Doesn't the command below do that?

"For Count1 = 0 to 10"

[dhouston]

Why? Doesn't the command below do that?

"For Count1 = 0 to 10"

He probably meant Checksum=0 before entering the loop.

[mackrackit]

He probably meant Checksum=0 before entering the loop.

Yup. Sorry about that.

[retepsnikrep]

Thanks for that. I have corrected my program.

I do not load 'checksum' with 0 because I load it with one of the packet header characters $87 or $AA before I call the 'Calcsum' routine

'Checksum' then already contains the first byte (header) of the packet when it enters, it then adds the content of the array 0-9 to the byte and does the checksum thing storing the result in position 10. So the packet is twelve bytes in all when sent out.

$87 header + 10 data bytes from array + byte 11 from array which is calculated checksum (sum of previous 11 bytes inc header byte)

I am collecting the checksum when reading in the data at the moment (and ignoring it) I will probably do the caluclation on it as well soon to make sure the incomming data is valid before I start messing about with it!!

Thanks for all your help so far.

[retepsnikrep]

Hmm, my checksum routine does not work and gives $ff as the last byte when using this data which I think is wrong.



My code is here any thoughts?

'-------------------------------------
' PBP BCM CODE 25/10/09 V.15 8mhz
'-------------------------------------

@ DEVICE PIC16F88,INTRC_OSC_NOCLKOUT
@ DEVICE PIC16F88,PROTECT_OFF
@ DEVICE PIC16F88,WDT_ON
@ DEVICE PIC16F88,PWRT_ON
@ DEVICE PIC16F88,MCLR_ON
@ DEVICE PIC16F88,BOD_OFF
@ DEVICE PIC16F88,LVP_OFF
@ DEVICE PIC16F88,CPD_OFF
@ DEVICE PIC16F88,DEBUG_OFF
@ DEVICE PIC16F88,CCPMX_OFF

DEFINE OSC 8 			'Set oscilator speed to 8mHz 
OSCCON=%01111000 		'8 Mhz

'DEFINE OSC 4 			'Set oscilator speed to 4mHz  
'OSCCON =%01100000		'4 Mhz
 
DEFINE HSER_BAUD 9600		'Set Baud rate to 9600bps
DEFINE HSER_BITS 9		'Set to 9 bit mode
DEFINE HSER_EVEN 1		'Set Even Parity
DEFINE HSER_CLROERR 1 		'Clear overflow error automatically

ANSEL = 0 			'ALL DIGITAL
CMCON = 7 			'COMPARATORS OFF
INTCON = 0 			'Disable interrupts
TRISB = %00000100 		'SET PORTB RB2(RX) as input, others to OUTPUT
TRISA = %11111111 		'SET PORTA AS INPUTS

'Variables

BCMDATA VAR BYTE[11]		'Define BCMDATA as a byte array (11 Bytes) 
Count1 VAR BYTE			'Define Count1 as a byte variable (Used in For/Next Loops)
CheckSum VAR BYTE		'Define CheckSum as a byte variable
Led1 VAR PORTB.0		'Define PortB.0 as Led1
Led2 VAR PORTB.1		'Define PortB.1 as Led2

'Constants


'Main Program Start

Commloop: 					'Start of Communications Loop

	HSERIN [WAIT($87), STR BCMDATA\11]	'Wait for packet start $87 then Receive 11 bytes into array BCMDATA
	
    BCMDATA[2] = $15            'Load Soc Byte with $15 (19 Bars)
    BCMDATA[3] = $6F	        'Load Soc Byte with $6F (19 Bars)
	CheckSum = $87				'Load Checksum with packet start byte value
	Gosub CalcSum				'Gosub CalcSum to Calculate Checksum 

	HSEROUT [$87,str BCMDATA\11]		'Transmit 12 bytes inc packet start byte $87
		
	HSERIN [WAIT($AA), STR BCMDATA\11]	'Wait for packet start $AA then Receive 11 bytes into array BCMDATA           	
	'CheckSum = $AA				'Load Checksum with packet start byte value
	'Gosub CalcSum				'Gosub CalcSum to Calculate Checksum 

	HSEROUT [$AA,str BCMDATA\11]		'Transmit 12 bytes inc packet start byte $AA

	goto CommlooP			'Goto Loop      
    
CalcSum:					'Calculate Packet CheckSum Routine
	
	For Count1 = 0 to 9			'For Count1 = 0 to 9 (Start 10 byte loop)
	CheckSum = CheckSum + BCMDATA[Count1]	'Add Bytes
	Next Count1				'Repeat until 10 bytes added
	CheckSum = NOT CheckSum			'Not CheckSum
	CheckSum = CheckSum + 1			'Add 1 to CheckSum
	BCMDATA[10] = CheckSum AND $7F 		'AND result
	Return					'Return 	


END

My understanding of how the checksum is generated comes from this info.

"Here's what I figured out so far: There are basically 10 data bytes per message. Before the first is the message type (AA or 87), and after the last is the checksum. You can compute it by adding the other 11 bytes, negating that (2's complement), then and'ing by 0x7f.
It makes the entire message add to 0 when you and by 0x7f."


And here is an known good sample.

0x87,0x40,0x58,0x15,0x6E,0x10,0x01,0x32,0x2F,0x2F, 0x04,0x39

Checksum byte is 0x39 at end.


Ooppps I think I have been an idiot and included the AND part in my routine which should not be there and in fact is done by the receiving device to see if the result is 0!!!

[dhouston]

If I define an array thus.

BCMDATA VAR BYTE[11]		'Define BCMDATA as a byte array (11 Bytes)

I get an array 11 bytes long and the address of the first byte is

BCMDATA[0] and the last BCMDATA[10] ?

Is that correct.

Correct.

Now onto for next loops.

CalcSum:					'Calculate Packet CheckSum Routine
	
	For Count1 = 0 to 10			'For Count1 = 0 to 10 (Start 11 byte loop)
	CheckSum = CheckSum + BCMDATA[Count1]	'Add Bytes
	Next Count1				'Repeat until 11 bytes added
	CheckSum = NOT CheckSum			'Not CheckSum
	CheckSum = CheckSum + 1			'Add 1 to CheckSum
	BCMDATA[10] = CheckSum AND $7F 		'AND result
	Return					'Return

In this code how many times does it complete?
And on the first pass through the loop Count1 =0 does it not?
And on the last pass through the loop Count1 = 9 or 10

So if count1 = 9 it goes through the loop, if it = 10 it jumps over it?

It goes through the loop 11 times (0-10) with Count1=10 during the final pass. When it exits the loop, Count1=11. The loop counter is incremented and tested at the bottom of a For/Next loop. The test occurs at the top of a While/Wend loop.

As written, your code writes a value to BCMDATA[10] in the loop and then overwrites BCMDATA[10] after exiting the loop. I suspect this is not what you want.

While the following link is written for Visual Basic, I think all versions of Basic work the same way.

• http://msdn.microsoft.com/en-us/libr...8VS.71%29.aspx