9
ATA6870-DK10 [APPLICATION NOTE]
9228C–AUTO–02/15
5.
Features of the Atmel ATmega32HVB
Since the Atmel
®
ATmega32HVB is a part of the Atmel AVR
®
family which is dedicated to battery management there are
several special features such as coulomb counting and the control of the two charge/discharge MOSFETs.
5.1
Coulomb Counter
The coulomb counter ADC runs on a different clock than the CPU. This clock is slower and therefore several things have to
be kept in mind before using it. Writing several registers in sequence takes a long time depending on the delays between
each write cycle. A possible solution is given in the supplied software example:
The Update Busy (CADUB) bit in CADSRA is cleared and written by hardware.
5.2
Charging/Discharging FETs
The two FETs are controlled by an N-channel FET driver. The pins (OC and OD) are designed for outputting a high voltage
of approx. 13V. The status of the pins is controlled by software via the FCSR - FET control and status register.
The example above implements an easy method to enable or disable the two FETs independently of each other. For more
information, see the Atmel ATmega32HVB datasheet page 148ff.
C Code Example
void CCinit(){
CADRCC = RCC_CADRCC;
while(CADCSRA & (1 << CADUB));
CADRDC = RDC_CADRDC;
while(CADCSRA & (1 << CADUB));
SETBIT(CADCSRB,1<<CADRCIE);
while(CADCSRA & (1 << CADUB));
SETBIT(CADCSRC,RCC_DIVIDEDSZ<<CADVSE);
while(CADCSRA & (1 << CADUB));
// Charge Threshold
// Discharge Threshold
// Interrupt Enable
// Voltage Scaling
SETBIT(CADCSRA,((1<<CADEN)|(1<<CADSE)|(RCC_CONVERSIONPERIOD<<1)));
while(CADCSRA & (1 << CADUB));
}
// ADC Enable, RCC Mode, Sampling
// Interval
C Code Example
void Configure_Fet(unsigned char Fet){
if(Fet&0x01)
SETBIT(FCSR, (1<<DFE));
else
CLEARBIT(FCSR,(1<<DFE));
if(Fet&0x02)
SETBIT(FCSR,(1<<CFE));
else
CLEARBIT(FCSR,(1<<CFE));
}
