Basic stamp & Linux: how to read data on serial port?
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Posts: 2
Dear forum,
I know this question has been raised several times but I haven't found the answer.
I have a quite extensive experience with Linux/POSIX C API for serial communication (tio, read, write and so on) but I'm a newbie to Basic Stamp. Despite my efforts I have not succeeded in communicating with my BS2e in C under Linux.
I would like to read data from a CMP03 device (connected via I2C) on the PC .
The PBASIC program seems OK (it runs under windows with Parallax soft). By the way it doesn't work with Hyper Terminal under windows so I guess it's a matter of serial port configuration.
The program waits for a 'j' and then outputs the bearing followed by CR ('\r' in C).
The basic stamp is plugged under /dev/ttyUSB0 (permissions are OK).
I have configured the tio to use baudrate 9600 and 8N1.
Writing 'j' on the port seems ok but I can't read data. My best trials returned 'j' (the very same things that I have input).
Questions:
1) Do I need to do disable/enable the DTR and RTS bits? Those seems to be disabled by Stamp Editor.
2) Can I use the canonical mode?
3) The documentation of SERIN and SEROUT talks about INVERTED polarity. What's this?
I must confess I'm a bit lost. Any help would be appreciated. Thanks in advance.
Mathieu
I know this question has been raised several times but I haven't found the answer.
I have a quite extensive experience with Linux/POSIX C API for serial communication (tio, read, write and so on) but I'm a newbie to Basic Stamp. Despite my efforts I have not succeeded in communicating with my BS2e in C under Linux.
I would like to read data from a CMP03 device (connected via I2C) on the PC .
The PBASIC program seems OK (it runs under windows with Parallax soft). By the way it doesn't work with Hyper Terminal under windows so I guess it's a matter of serial port configuration.
The program waits for a 'j' and then outputs the bearing followed by CR ('\r' in C).
'{$STAMP BS2}
'***********************************************************
'** **
'** I2C Routines for the Basic Stamp **
'** using the CMPS01 Compass Module **
'** **
'** Copyright 2002 - Devantech Ltd **
'** Commercial use of this software is prohibited **
'** Private and educational use only is permitted **
'** **
'** Written by Gerald Coe - January 2002 **
'** **
'** This Code has been Tested on BS2 and BS2p **
'** It should work equally well on the BS2e and BS2sx **
'** **
'** E.T.I.S Neurocybernetic 10/2004 **
'** Modified by N.Cuperlier for the Blue Robot **
'** **
'***********************************************************
SDA con 8 ' I2C data
SCL con 9 ' I2C clock
SDAin var in8
SDAout var out8
SDAdir var dir8
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:
'** wait for an serial input "J" to send back the value of the compass
' debug 1,0,0, "Entrez J pour lire la valeur de la boussole"
serin 16,16468,[noparse][[/noparse]WAIT("j")] '
I2cAddr = $c0 ' CMPS01 Compass module address
I2cReg = 1 ' Bearing as 0-255 (BRAD)
gosub I2cByteRead
'**debug 2,0,0, "Compass Bearing (0-255 BRAD) ", dec3 I2cData
I2cReg = 2 ' Bearing as 0-359.9 degrees
gosub I2cWordRead
'**debug 2,0,1, "Compass Bearing (0-359 Degrees ", dec3 I2cData/10
serout 16,16468,[noparse][[/noparse]DEC I2cData/10, CR]
goto Main
Baddata:
'debug 1,0,0, "wait:",CR
sleep 2
goto Main
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
The basic stamp is plugged under /dev/ttyUSB0 (permissions are OK).
I have configured the tio to use baudrate 9600 and 8N1.
Writing 'j' on the port seems ok but I can't read data. My best trials returned 'j' (the very same things that I have input).
Questions:
1) Do I need to do disable/enable the DTR and RTS bits? Those seems to be disabled by Stamp Editor.
2) Can I use the canonical mode?
3) The documentation of SERIN and SEROUT talks about INVERTED polarity. What's this?
I must confess I'm a bit lost. Any help would be appreciated. Thanks in advance.
Mathieu
Comments
First I have used C code to reset the basic stamp (thanks to open source) by playing with ioctl().
Second I have slightly modified the code to insert a pause after the SEROUT command and an explicit message after initialization.
All in all this seems to work. If somebody have a better way to do I'm still opened...
Mathieu