Devantech''s SRF08 and BS2

Archiver

Hi,

I have an odd problem reading one of the srf08 sonar Module with a BS2. The
sensor responses to distance but It halts after a time and gets stuck in
zero, as If some invisible object were really near, then It does not read
anymore. The sensor wakes up again only when I put an object very close.
The code I am using is the demo from Devantech below and I am also putting
10k pull up resistors on the SCL and SDA lines to 5v.

Thank you for your advice,

SCL con 12 ' I2C clock
SDA con 11 ' I2C data
SDAin var in11
SDAout var out11 ' To change the pins used, alter these 5 lines
SDAdir var dir11 ' The 4 SDA numbers must be the same, of course
loop var byte ' just a looping counter
I2cBuf var byte ' I2c read/write buffer
I2cAddr var byte ' Address of I2C device
I2cReg var byte ' Register number within I2C device
I2cData var word ' Data to read/write
I2cAck var bit ' Acknowledge bit
Main:
' ______________1st SRF08 Ranger
I2cAddr = $e0
I2cReg = 0
I2cData = 81 ' Ranging command - 80 for inches, 81 for cm, 82 for uS
gosub I2cByteWrite
pause 70 ' wait for ranging to complete
I2cReg = 1 ' address of light sensor register
gosub I2cByteRead
debug 2,0,0, "Light Sensor1 ", dec3 I2cData
I2cReg = 2 ' address of first ranging result
gosub I2cWordRead
debug 2,0,1, "Range1 ", dec4 I2cData
serout 10,16468, [noparse][[/noparse]dec4 I2cData]
'
serout 10,16468, [noparse][[/noparse]"--"]
'

---

\

---

' I2C subroutines follow
'

---

\

---

I2cByteWrite: ' writes I2cData.lowbyte to I2cReg at I2cAddr
gosub I2cStart
I2cBuf = I2cAddr
gosub I2cOutByte ' send device address
I2cBuf = I2cReg
gosub I2cOutByte ' send register number
I2cBuf = I2cData.lowbyte
gosub I2cOutByte ' send the data
gosub I2cStop
return
I2cWordWrite: ' writes I2cData to I2cReg at I2cAddr
gosub I2cStart
I2cBuf = I2cAddr
gosub I2cOutByte ' send device address
I2cBuf = I2cReg
gosub I2cOutByte ' send register number
I2cBuf = I2cData.highbyte
gosub I2cOutByte ' send the data - high byte
I2cBuf = I2cData.lowbyte
gosub I2cOutByte ' send the data - low byte
gosub I2cStop
return
I2CByteRead:
gosub I2cStart
I2cBuf = I2cAddr
gosub I2cOutByte ' send device address
I2cBuf = I2cReg
gosub I2cOutByte ' send register number
gosub I2cStart ' repeated start
I2cBuf = I2cAddr | 1
gosub I2cOutByte ' send device address (with read set)
I2cAck = 0 ' send Nak
gosub I2cInByte
I2cData.lowbyte = I2cBuf ' read the data
I2cData.highbyte = 0
gosub I2cStop
return
I2CWordRead:
gosub I2cStart
I2cBuf = I2cAddr
gosub I2cOutByte ' send device address
I2cBuf = I2cReg
gosub I2cOutByte ' send register number
gosub I2cStart ' repeated start
I2cBuf = I2cAddr | 1
I2cAck = 1 ' send Ack
gosub I2cOutByte ' send device address (with read set)
gosub I2cInByte
I2cData.highbyte = I2cBuf ' read the data
I2cAck = 0 ' send Nak
gosub I2cInByte
I2cData.lowbyte = I2cBuf
gosub I2cStop
return
I2cOutByte:
shiftout SDA, SCL, MSBFIRST, [noparse][[/noparse]I2cBuf]
input SDA
high SCL ' clock in the ack' bit
low SCL
return
I2cInByte:
shiftin SDA, SCL, MSBPRE, [noparse][[/noparse]I2cBuf]
SDAout = 0
SDAdir = I2cAck
high SCL ' clock out the ack' bit
low SCL
input SDA
return
I2cStart ' I2C start bit sequence
high SDA
high SCL
low SDA
low SCL
return
I2cStop: ' I2C stop bit sequence
low SDA
high SCL
high SDA
return

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