GCBASIC / Discussion / Help: When zero is not zero! 00 is not 0 -- a deicmal error

Two Issues:

@ 16 Mhz we get a bus error on some writes, @ 4Mhz it is not an issue -- I will need explore that. And only on the triple write sequence. It occurs on both 00 or 0, so it is not related.
00 [decimal] is not 0

xb= 00 is not zero but 0x13
xb= 0 is zero

Good

main:
xb = 0
i2cWrite (IO_Chip6, IODIRA, xb)  ' make portA outputs
i2cWrite (IO_Chip6, IODIRB, xb)  ' make portB outputs

BAD!

main:
xb = 00
i2cWrite (IO_Chip6, IODIRA, xb)  ' make portA outputs
i2cWrite (IO_Chip6, IODIRB, xb)  ' make portB outputs

not0
not0

[a $50 logic analyzer: http://dangerousprototypes.com/docs/Open_Bench_Logic_Sniffer]

i2c data dump - .csv format

"index","start-time","end-time","event?","event-type","data"
"0","-42.000 ?s","-42.000 ?s","true","START",""
"1","-38.000 ?s","84.000 ?s","false","","L"
"2","92.000 ?s","92.000 ?s","true","ACK",""
"3","98.000 ?s","228.000 ?s","false",""," "
"4","236.000 ?s","236.000 ?s","true","ACK",""
"5","244.000 ?s","372.000 ?s","false","",""
"6","380.000 ?s","380.000 ?s","true","ACK",""
"7","402.000 ?s","402.000 ?s","true","BUS-ERROR",""
"8","402.000 ?s","402.000 ?s","true","STOP",""
"9","414.000 ?s","414.000 ?s","true","START",""
"10","418.000 ?s","540.000 ?s","false","","L"
"11","548.000 ?s","548.000 ?s","true","ACK",""
"12","554.000 ?s","684.000 ?s","false","",""
"13","692.000 ?s","692.000 ?s","true","ACK",""
"14","698.000 ?s","828.000 ?s","false","",""
"15","836.000 ?s","836.000 ?s","true","ACK",""
"16","858.000 ?s","858.000 ?s","true","STOP",""
"17","870.000 ?s","870.000 ?s","true","START",""
"18","874.000 ?s","996.000 ?s","false","","L"
"19","1.004 ms","1.004 ms","true","ACK",""
"20","1.012 ms","1.140 ms","false","",""
"21","1.148 ms","1.148 ms","true","ACK",""
"22","1.154 ms","1.280 ms","false","","ÿ"
"23","1.288 ms","1.288 ms","true","ACK",""
"24","1.312 ms","1.312 ms","true","STOP",""
"25","1.324 ms","1.324 ms","true","START",""
"26","1.328 ms","1.450 ms","false","","L"
"27","1.458 ms","1.458 ms","true","ACK",""
"28","1.464 ms","1.592 ms","false","",""
"29","1.600 ms","1.600 ms","true","ACK",""
"30","1.608 ms","1.734 ms","false","","ÿ"
"31","1.742 ms","1.742 ms","true","ACK",""

The Code

-------------------------------------------------------------------
;Chip Settings
#chip 16F1829, 16

;Include files (Libraries)
;#include <glcd.h>

;Defines (Constants)
#define LCD_IO 4
#define LCD_DB4 PORTC.0
#define LCD_DB5 PORTC.1
#define LCD_DB6 PORTC.2
#define LCD_DB7 PORTC.3
#define LCD_Enable PORTC.4
#define LCD_RS PORTC.5
#define LCD_NO_RW 'Needed when RW is grounded

'I2C settings
#define I2C_MODE Master
#define I2C_DATA PORTb.5
#define I2C_CLOCK PORTb.7
#define I2C_Read_BIT  = 1
#define I2C_Write_BIT = 0

'Constants
' MCP23017 details
#define IO_Chip6    0x26 ' NOT Shifted -- 0b01001100 ' the value $26 is shifted left 1 becuse of The RW bit: $26 << 1 = $4C
' use bank0 mode addresses
#define IODIRA  0x00  ' default is INput  0= out 1= in
#define IODIRB  0x01
#define IPOLA   0x02  ' input polarity 0= normal, 1= inverted
#define IPOLB   0x03
#define GPINTENA    0x04  ' Allow interrupt on change
#define GPINTENB    0x05
#define DEFVALA 0x06  ' default value BEFORE interrupt [for easy compare]
#define DEFVALB 0x07
#define INTCONA 0x08 ' I/O EXPANDER CONFIGURATION .2 1= Open Drain [wire together interrupts]
#define INTCONB 0x09
#define IOCON   0x0A ' 0= Interrupt on change , 1= Interrupt on Difference
#define IOCON   0x0B
#define GPPUA   0x0C ' weak pull up resistors [~100kOhhm] very handy
#define GPPUB   0x0D
#define ITFA    0x0E ' who done it, the interrupt
#define ITFB    0x0F
#define INTCAPA 0x10 ' Saves the event that caused the interrupt
#define INTCAPB 0x11
#define GPIOA   0x12 ' the IO port
#define GPIOB   0x13
#define OLATA   0x14 ' the LATCH of the IO port see docs
#define OLATB   0x15

;Variables
Dim xB            As byte
Dim i2cDevice    As byte
Dim i2cAddress   As byte
Dim i2cData      As byte

' Fixes a problem with LCD not working - thanks Kent!
' Don't assume that the digital is setup correctly.
clrf ANSELa
clrf ANSELb
clrf ANSELc

main:

xb = 0
i2cWrite (IO_Chip6, IODIRA, xb)  ' make portA outputs
i2cWrite (IO_Chip6, IODIRB, xb)  ' make portB outputs

'xb = 255 '0xFF
xb = 0xFF
i2cWrite (IO_Chip6, GPIOA, xb)  ' turn all pins on
i2cWrite (IO_Chip6, GPIOB, xb)  ' turn all pins on
Wait 250 ms

xb = 0xAA '170
i2cWrite (IO_Chip6, GPIOA, xb)  ' swap pins on/off
i2cWrite (IO_Chip6, GPIOB, xb)  '
Wait 250 ms

xb = 0x55 '85 '
i2cWrite (IO_Chip6, GPIOA, xb)  ' swap pins on/off
i2cWrite (IO_Chip6, GPIOB, xb)  '
Wait 250 ms

xb =  0x00 '0 '
i2cWrite (IO_Chip6, GPIOA, xb)  ' turn all pins oFF
i2cWrite (IO_Chip6, GPIOB, xb)  ' turn all pins oFF
Wait 250 ms

cls
Locate 0,2
Print " wrote i2c "

'for xb = 1 to 5
'Locate 0,xb
'Print " Hello World "
'print xb
'Wait 100 ms
'next xb

goto main
end

sub i2cWrite (i2cDevice, i2cAddress, i2cData) #NR

i2cDevice = i2cDevice *2 ' *2 = << 1 ' is shifted left 1 because of The RW bit: $26 << 1 = $4C
 i2cstart
  I2CSend i2cDevice + I2C_Write_BIT  ' Who + how
  I2CSend i2cAddress             ' Where to put it
  I2CSend i2cData                ' What to put there
 I2CStop
end sub

'not tested yet ....
Function i2cRead (i2cDevice, i2cAddress)
i2cDevice = i2cDevice *2 ' *2 = << 1 ' is shifted left 1 because of The RW bit: $26 << 1 = $4C
 i2cstart
  I2CSend     i2cDevice + I2C_Read_BIT   ' Who + how
  I2CSend     i2cAddress             ' Where to GET it
  I2CReceive  i2cData                ' What to GET from there
 I2CStop
i2cRead  =  i2cData
end function

Last edit: ofuzzy1 2013-09-23