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i2c_timer_pwm.c initial PWM initialization.

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This commit is contained in:
kevin.larke 2019-07-14 11:15:38 -04:00
parent b018a107d2
commit 04dc59ee48
2 changed files with 55 additions and 22 deletions
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2
control/tiny/Makefile
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@ -3,7 +3,7 @@ TTY=/dev/ttyACM0
endif endif
ifndef TARGET ifndef TARGET
TARGET=blink TARGET=i2c_timer_pwm
endif endif
MCU=attiny85 MCU=attiny85

75
control/tiny/i2c_timer_pwm.c
View File

@ -9,17 +9,23 @@
#define I2C_SLAVE_ADDRESS 0x8 // the 7-bit address (remember to change this when adapting this example) #define I2C_SLAVE_ADDRESS 0x8 // the 7-bit address (remember to change this when adapting this example)
enum enum
{ {
kCS13_10_idx = 0, // Timer 1 Prescalar (CS13,CS12,CS11,CS10) from Table 12-5 pg 89 kCS13_10_idx = 0, // Timer 1 Prescalar (CS13,CS12,CS11,CS10) from Table 12-5 pg 89
kOCR1C_idx = 1, // OCR1C timer match value kTmr0_Coarse_idx = 1, // count of times timer0 count to 255 before OCR1C is set to Tmr0_Minor
kTmr0_Fine_idx = 2, // OCR1C timer match value
kPWM_Duty_idx = 3, //
kPWM_Freq_idx = 4, // 1-4 = clock divider=1=1,2=8,3=64,4=256,5=1024
}; };
volatile uint8_t ctl_regs[] = volatile uint8_t ctl_regs[] =
{ {
0x0f, // clk/16384 0x0f, // 0 (0-15) timer prescalar 0=stop, prescaler = pow(2,val-1), 0=stop,1=1,2=2,3=4,4=8,....14=8192,15=16384 pre_scaled_hz = clock_hz/value
244, // OCR1C 0, // 1 (0-255) Tmr0_Coarse count of times timer count to 255 before loading Tmr0_Minor for final count.
244, // 2 (0-254) Tmr0_Fine OCR1C value on final phase before triggering timer
127, // 3 (0-255) Duty cycle
4, // 4 (1-4) PWM Frequency (clock pre-scaler)
}; };
// Tracks the current register pointer position // Tracks the current register pointer position
@ -28,20 +34,42 @@ const uint8_t reg_size = sizeof(ctl_regs);
ISR(TIMER1_OVF_vect) ISR(TIMER1_OVF_vect)
{ {
PINB = _BV(PINB4); // writes to PINB toggle the pins PINB = _BV(PINB4) + _BV(PINB1); // writes to PINB toggle the pins
} }
void timer_init()
void timer1_init()
{ {
TIMSK &= ~_BV(TOIE1); // Disable interrupt TIMER1_OVF TIMSK &= ~_BV(TOIE1); // Disable interrupt TIMER1_OVF
OCR1A = 255; // Set to anything greater than OCR1C (the counter never gets here.) OCR1A = 255; // Set to anything greater than OCR1C (the counter never gets here.)
TCCR1 |= _BV(CTC1); // Reset TCNT1 to 0 when TCNT1==OCR1C TCCR1 |= _BV(CTC1); // Reset TCNT1 to 0 when TCNT1==OCR1C
TCCR1 |= _BV(PWM1A); // Enable PWM A TCCR1 |= _BV(PWM1A); // Enable PWM A
TCCR1 |= ctl_regs[kCS13_10_idx] & 0x0f; TCCR1 |= ctl_regs[kCS13_10_idx] & 0x0f; //
OCR1C = ctl_regs[kOCR1C_idx]; OCR1C = ctl_regs[kTmr0_Fine_idx];
TIMSK |= _BV(TOIE1); // Enable interrupt TIMER1_OVF TIMSK |= _BV(TOIE1); // Enable interrupt TIMER1_OVF
} }
void pwm0_update()
{
OCR0B = ctl_regs[kPWM_Duty_idx]; // 50% duty cycle
TCCR0B |= ctl_regs[kPWM_Freq_idx]; // PWM frequency pre-scaler
}
void pwm0_init()
{
//WGM[1:0] = 3 (TOP=255)
// OCR0B = duty cycle (0-100%)
// COM0A[1:0] = 2 non-inverted
//
TCCR0A |= 0x20 + 3; // 0x20=non-inverting 3=WGM bits Fast-PWM mode (0=Bot 255=Top)
TCCR0B |= 0x00 + 4; // 3=256 pre-scaler 122Hz=1Mghz/(v*256) where v=64
pwm0_update();
DDRB |= _BV(DDB1);
}
/** /**
@ -74,14 +102,14 @@ void on_request()
* them directly, * them directly,
*/ */
void on_receive( uint8_t howMany ) void on_receive( uint8_t byteN )
{ {
if (howMany < 1) if (byteN < 1)
{ {
// Sanity-check // Sanity-check
return; return;
} }
if (howMany > TWI_RX_BUFFER_SIZE) if (byteN > TWI_RX_BUFFER_SIZE)
{ {
// Also insane number // Also insane number
return; return;
@ -90,24 +118,28 @@ void on_receive( uint8_t howMany )
// get the register index to read/write // get the register index to read/write
reg_position = usiTwiReceiveByte(); reg_position = usiTwiReceiveByte();
howMany--; byteN--;
// If only one byte was received then this was a read request // If only one byte was received then this was a read request
// and the buffer pointer (reg_position) is now set to return the byte // and the buffer pointer (reg_position) is now set to return the byte
// at this location on the subsequent call to on_request() ... // at this location on the subsequent call to on_request() ...
if (!howMany) if (!byteN)
{ {
return; return;
} }
// ... otherwise this was a write request and the buffer // ... otherwise this was a write request and the buffer
// pointer is now pointing to the first byte to write to // pointer is now pointing to the first byte to write to
while(howMany--) while(byteN--)
{ {
ctl_regs[reg_position] = usiTwiReceiveByte(); ctl_regs[reg_position] = usiTwiReceiveByte();
if(reg_position == kCS13_10_idx || reg_position == kOCR1C_idx ) if( kCS13_10_idx <= reg_position && reg_position <= kTmr0_Fine_idx )
timer_init(); timer1_init();
if( kPWM_Duty_idx <= reg_position && reg_position <= kPWM_Freq_idx )
pwm0_update();
reg_position++; reg_position++;
if (reg_position >= reg_size) if (reg_position >= reg_size)
@ -124,11 +156,12 @@ int main(void)
{ {
cli(); // mask all interupts cli(); // mask all interupts
DDRB |= _BV(DDB4); // setup PB4 as output DDRB |= _BV(DDB4) + _BV(DDB1); // setup PB4 as output
PORTB &= ~_BV(PINB4); PORTB &= ~(_BV(PINB4) + _BV(PINB1));
timer_init();
timer1_init();
pwm0_init();
// setup i2c library // setup i2c library
usi_onReceiverPtr = on_receive; //on_receive; usi_onReceiverPtr = on_receive; //on_receive;
usi_onRequestPtr = on_request; usi_onRequestPtr = on_request;