Difference between revisions of "Temperature sensor example"

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Line 12: Line 12:
$ui -W 81:1000
$ui -W 81:1000
$ui -w 82:6
$ui -w 82:6
$io -w 80:2
$ui -w 80:2


The above script is written for the SPI version of the board. The commented out like is for the i2c-version. So activate that line if you have the i2c version (remove the comment marker).
The above script is written for the SPI version of the board. The commented out like is for the i2c-version. So activate that line if you have the i2c version (remove the comment marker).

Latest revision as of 14:48, 7 September 2015

initialization

The following is a script that I use to initialize the temperature sensors for the rpi_ui board.

#!/bin/sh
ui="bw_tool -a 94"
#ui="bw_tool -a 94 -I -D /dev/i2c-1"
$ui -w 70:c7 # internal tempsens with internal 1.1V as reference
$ui -w 71:c6 # external tempsens with internal 1.1V as reference
$ui -W 81:1000
$ui -w 82:6
$ui -w 80:2

The above script is written for the SPI version of the board. The commented out like is for the i2c-version. So activate that line if you have the i2c version (remove the comment marker).

readout

The following is a script that shows the temperature on stdout. I call this script "showtemp".


#!/bin/sh
# 
#
# Set the number of samples to 64, and shift by 0, or set the 
# number of samples to 4096 and shift by 6. The latter is recommended!
#
adcmaxval=65520
#adcmaxval=1023
#
# MCP9700 degrees per volt. 
vperdeg=0.010
#refvoltage=4.9000
refvoltage=1.1000
# mcp offset voltage is 500mv at 0 deg. At 0.010 volt per deg that comes to 
# 50 degrees C. 
offset=50
#
#
# 60 adc channel 0, direct value (0-1023)
# 68 adc channel 0, averaged value (0-65520 with nsamp=4096, shift=6)
# 61 adc channel 1, direct value (0-1023)
# 69 adc channel 1, averaged value (0-65520 with nsamp=4096, shift=6)
register_to_read=69

#
# settings are done, now the preparations. 
convfactor=`(echo scale = 10 ; echo obase=16;echo $refvoltage / $vperdeg / $adcmaxval ) | bc`
offsethex=`(echo obase=16; echo scale=3;echo $offset) | bc `


# now do the real deal. 
rawtemp=`sudo bw_tool -s 100000 -a 94 -R $register_to_read:s | tr a-z A-Z`
(echo ibase=16; echo scale=3;echo $rawtemp \* $convfactor - $offsethex)  | bc

display

The following clears the screen and then shows the temperature.

bw_tool -a 94 -w 10:0
bw_tool -a 94 -t "temp: "`./showtemp`