The BAT_MON pin is connected to ADC7 internally as shown on pg 1
of the mica2 schematic. It took me a little while to figure it
out because the logic is wonky. What you are reading is a
fixed voltage reference. It 'works' because the ADC reference
is the battery itself, so as the bat drops the ref seems to
rise in value...at least that's the conclusion I came to...
Assuming that you are not getting a trustworthy Voltage reading,
I think your problem is calling BattControl.stop() right after
starting your conversion. This shuts off the BAT_MON pin which
powers the voltref, possibly before the ADC has had time to
sample it. I'm also not sure what the StdControl.start() is for
in that method.
If power is an issue then you might want to do the BattControl.start()
in the getData() and the stop() in dataReady().
And...now that I look, are you calling ADC.getData() anywhere?
My usual layout is to get the timer going in the main start()
and have the timer.fired() initiate a conversion by calling
some getData(). Then either round-robin each ADC in the fired()
or chain them through the dataReady()s.
If your sensor is powered from the same battery and is reasonably
linear with voltage (it looks like your calc assumes that), then
why do you need to adjust the readings at all?
One last quibble: floats are expensive...you could do everything
in fixed point...but that's just me.
MS
Amra Pasic wrote:
Hi all,
I'm trying to read the battery voltage to adjust my ADC scale on mica2
motes. I followed the instructions in User Manual to set the BAT_MON pin
high. What I am not really sure is do I have to connect ADC7 pin to
BAT_MON or this is somehow done internally?
Here is the example of my code that doesn't work (I tried to follow the
examples already available). Can anyone point out what is wrong with it?
I am using this file to read the pressure using TinyDB application.
I added the following to my sensorboard file:
#define MAKE_BAT_MONITOR_OUTPUT() sbi(DDRA, 5)
#define MAKE_BAT_ADC_INPUT() cbi(DDRF, 7)
#define SET_BAT_MONITOR() sbi(PORTA, 5)
#define CLEAR_BAT_MONITOR() cbi(PORTA, 5)
I wired this in my Pressure.nc file
PressureM.BattControl -> Voltage;
PressureM.ADCBATT -> Voltage;
And my whole PressureM.nc file is:
includes sensorboard;
module PressureM {
provides {
interface StdControl;
interface ADC;
}
uses {
interface Leds;
// Battery
interface ADC as ADCBATT;
interface StdControl as BattControl;
//Pressure
interface ADC as Pressure;
interface ADCControl;
interface Timer;
}
}
implementation
{
float Vbatt;
float P;
uint16_t press;
command result_t StdControl.init() {
call Leds.init();
call BattControl.init();
call ADCControl.bindPort(TOS_ADC_PRESSURE_PORT,
TOSH_ACTUAL_PRESSURE_PORT);
TOSH_MAKE_PRESSURE_CTL_OUTPUT();
TOSH_CLR_PRESSURE_CTL_PIN(); //n-channel off --> p-channle off
//TOSH_SET_PRESSURE_CTL_PIN(); //n-channel on --> p-channle on
dbg(DBG_BOOT, "PRESSURE initialized.\n");
return call ADCControl.init();
}
command result_t StdControl.start() {
call BattControl.start();
TOSH_SET_PRESSURE_CTL_PIN(); //n-channel on --> p-channle on
// TOSH_CLR_PRESSURE_CTL_PIN(); //n-channel off --> p-channle off
return SUCCESS;
}
command result_t StdControl.stop() {
TOSH_CLR_PRESSURE_CTL_PIN(); //n-channel off --> p-channle off
// TOSH_SET_PRESSURE_CTL_PIN(); //n-channel on --> p-channle on
return SUCCESS;
}
event result_t Timer.fired()
{
return SUCCESS;
}
async command result_t ADC.getData()
{
call StdControl.start();
// SET_BAT_MONITOR(); //already done in VoltageM.nc
call ADCBATT.getData(); //get the battery voltage;
// CLEAR_BAT_MONITOR(); //already done in VoltageM.nc
call BattControl.stop();
call Timer.start(TIMER_ONE_SHOT, 12); //AP to extand PW duration
from 8ms to 20ms
//20ms
stabilisation
return call Pressure.getData();
}
default async event result_t ADC.dataReady(uint16_t data)
{
return SUCCESS;
}
async command result_t ADC.getContinuousData()
{
return FAIL;
}
async event result_t ADCBATT.dataReady(uint16_t data) {
Vbatt = 1.223*1024/data;
return SUCCESS;
}
async event result_t Pressure.dataReady(uint16_t data){
P = (float)(data)*Vbatt/1024.0;
P = (P/Vbatt + 0.32667)/0.01067; //kPa infineon
// P = (P/Vbatt + 0.095)/0.009; //kPa motorola
P = P*10; //kPa to mbar
press = (uint16_t)(P);
signal ADC.dataReady(press);
return SUCCESS;
}
}
------------------------------------------------------------------------
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