Texas Instruments AM335 Series Design Manual page 37

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DIY INA I2C Measurement
#!/bin/bash
#INA226 Registers
CONFIG_REG=0x0
SHUNTV_REG=0x1
BUSV_REG=0x2
#EVM Specific
declare -a INA_ADDRS=(0x41);
declare -a SUPPLIES=('VDD_MPU ');
declare -a RES=(0.001);
#Take shunt voltage measurements #Re-initialize INA226
i2cset -y 1 ${INA_ADDRS[0]} $CONFIG_REG 0x0080 w
i2cset -y 1 ${INA_ADDRS[0]} $CONFIG_REG 0xFF4F w
shuntv=$(i2cget -y 1 ${INA_ADDRS[0]} $SHUNTV_REG w)
let "temp = shuntv >> 8"
let "temp2 = shuntv << 8 | $temp"
let "shuntv = $temp2 & 0xffff"
let "neg_test = $shuntv & 0x8000"
if [ "$neg_test"
shuntv=0
fi
shuntv=$(echo "$shuntv*0.0025"
#Take bus voltage measurements #Re-initialize INA226
i2cset -y 1 ${INA_ADDRS[0]} $CONFIG_REG 0x0080 w
i2cset -y 1 ${INA_ADDRS[0]} $CONFIG_REG 0xFF4F w
busv=$(i2cget -y 1 ${INA_ADDRS[0]} $BUSV_REG w)
let "temp = $busv >> 8"
let "temp2 = $busv << 8 | $temp"
let "busv = $temp2 & 0xffff"
busv=$(echo "$busv*0.00125"
#Calculate power
current=$(echo "${shuntv}/${RES[0]}"
power=$(echo "${current}*${busv}"
#Output to console
printf "Supply\t\tRes (ohm)\tShunt (mV)\tBus (V)\t\tCurrent (mA)\tPower (mW)\n"
printf "%s\t%.3f\t\t%f\t%f\t%f\t%f\n" "${SUPPLIES[0]}" "${RES[0]}" "${shuntv}" "${busv}"
"${current}" "${power}"
SPRAC74A – February 2017 – Revised March 2017
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Example Source Code
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