changed from bs2e to bs2p, now I2C doesn't work!

electricbrewer

Hi, new guy here....

I'm having trouble with my I2C and DS1621 interface...

I was able to implement the nuts and volts DS1621 code for I2C on my basic stamp 2e, with 3 temp sensors running perfectly. I started to run out of program space so I figure that purchasing the 2p-24 stamp would eliminate all the extra code needed for the DS1621. I adjusted the code into this:

SDA PIN 8 ' SDA on 0; SCL on 1


'

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[noparse][[/noparse] Constants ]

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DevType CON %1001 << 4 ' Device type
DevAddr CON %111 << 1 ' address = %000 -> %111
Wr1621 CON DevType | DevAddr ' write to DS1621
Rd1621 CON Wr1621 | 1 ' read from DS1621
RdTemp CON $AA ' read temperature
RdCntr CON $A8 ' read counter
RdSlope CON $A9 ' read slope
StartC CON $EE ' start conversion
StopC CON $22 ' stop conversion
AccTH CON $A1 ' access high temp limit
AccTL CON $A2 ' access low temp limit
AccCfg CON $AC ' access config register
TempHi CON 25 ' 26C = ~77F
TempLo CON 22 ' 21C = ~72F
DegSym CON 176 ' degrees symbol

'

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[noparse][[/noparse] Variables ]

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tempIn VAR Word ' raw temp from DS1621
sign VAR tempIn.BIT8 ' - sign (after alignment)
halfC VAR tempIn.BIT0 ' half-degree C bit
tempC VAR Word ' temp in Celsius
tempF VAR Word ' temp in Fahrenheit
'

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[noparse][[/noparse] Initialization ]

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Setup:
I2COUT SDA, Wr1621, [noparse][[/noparse]AccCfg, %1010] ' set TOut = active high
PAUSE 1000 ' allow EE write
I2COUT SDA, Wr1621, [noparse][[/noparse]StartC] ' start continuous
PAUSE 1000

Set_Thermostat:
I2COUT SDA, Wr1621, [noparse][[/noparse]AccTH, TempHi] ' set high threshold
PAUSE 1000
I2COUT SDA, Wr1621, [noparse][[/noparse]AccTL, TempLo] ' set low threshold
PAUSE 1000

Demo_Screen:
DEBUG CLS,
"DS1621 Demo", CR,
"

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", CR,
DegSym, "C... ", CR,
DegSym, "F... "
'

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[noparse][[/noparse] Program Code ]

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Main:
DO
PAUSE 1000 ' delay between reads
GOSUB Get_Temp ' get current temperature
DEBUG CRSRXY, 6, 2, SDEC tempC, CLREOL, ' display
CRSRXY, 6, 3, SDEC tempF, CLREOL
LOOP
END
'

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[noparse][[/noparse] Subroutines ]

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Get_Temp:

I2COUT SDA, Wr1621, [noparse][[/noparse]RdTemp]
PAUSE 50
I2CIN SDA, Rd1621, [noparse][[/noparse]tempIn.HIGHBYTE, tempIn.LOWBYTE]
PAUSE 50
tempIn = tempIn >> 7 ' correct bit alignment
' Celsius
tempC = (tempIn / 2) | ($FF00 * sign)
' Fahrenheit
tempF = (tempIn | ($FF00 * sign)) + 110
tempF = tempF * 9 / 10 - 67 ' convert to F
RETURN
==============================================================

Now all I get is the Debug window showing up the two same numbers -1, and 30 after Celsius a Fahrenheit. Even when I unplug the temperature sensors completely and let the code run, it just does the same thing, whereas before if I didn't address the correct sensor right it wouldn't work.

Anyone have a clue why this would occur???

I really appreciate your help in saving a senior design student!!

Justin

electricbrewer

Well apparently I found my own solution eventually... I appears that I may have a model older than 2002 in which the I2C commands didn't implement the clock line bus hold.

Justin

Carl Hayes

Also your code says SDA is on 8, but your comment says it's on 0. Either is OK, but if you try it both ways they get jealous.

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· -- Carl, nn5i