Remove unnecessary pull-ups on inputs, open-drain output.
This commit is contained in:
Andrew Makousky
parent
652aab70ab
commit
e2483ddd59
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@ -109,12 +109,24 @@ volatile byte writeProtect = 0;
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#define shiftReadPB(output, bitNum, portBit) \
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bitWrite(output, bitNum, (PINB&_BV(portBit)) ? 1 : 0)
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void digitalWritePB(uint8_t pin, uint8_t val) {
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// Configure a pin to be an open-drain output, currently does nothing
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// as using digitalWriteOD() does all required setup and leaving the
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// pin as an input in the meantime is fine.
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#define configOutputOD(pin)
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// Digital write in an open-drain fashion: set as output-low for zero,
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// set as input-no-pullup for one.
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void digitalWriteOD(uint8_t pin, uint8_t val) {
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uint8_t bit = _BV(pin);
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if (val == 0)
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PORTB &= ~bit;
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else
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PORTB |= bit;
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// cli();
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if (val == 0) {
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DDRB |= bit;
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// PORTB &= ~bit;
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} else {
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DDRB &= ~bit;
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// PORTB &= ~bit;
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}
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// sei();
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}
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void setup(void) {
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@ -122,17 +134,17 @@ void setup(void) {
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// OUTPUT: The 1Hz square wave (used for interrupts elsewhere in the system)
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DDRB |= ONE_SEC_PIN;
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// INPUT_PULLUP: The processor pulls this pin low when it wants access
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// INPUT: The processor pulls this pin low when it wants access
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DDRB &= ~RTC_ENABLE_PIN;
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PORTB |= RTC_ENABLE_PIN;
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PORTB &= ~RTC_ENABLE_PIN;
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lastRTCEnable = PINB&(1<<RTC_ENABLE_PIN); // Initialize last value
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// INPUT_PULLUP: The serial clock is driven by the processor
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// INPUT: The serial clock is driven by the processor
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DDRB &= ~SERIAL_CLOCK_PIN;
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PORTB |= SERIAL_CLOCK_PIN;
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PORTB &= ~SERIAL_CLOCK_PIN;
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lastSerClock = PINB&(1<<SERIAL_CLOCK_PIN); // Initialize last value
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// INPUT_PULLUP: We'll need to switch this to output when sending data
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// INPUT: We'll need to switch this to output when sending data
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DDRB &= ~SERIAL_DATA_PIN;
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PORTB |= SERIAL_DATA_PIN;
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PORTB &= ~SERIAL_DATA_PIN;
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wdt_disable(); // Disable watchdog
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bitSet(ACSR, ACD); // Disable Analog Comparator, don't need it, saves power
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@ -161,11 +173,11 @@ void setup(void) {
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}
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void clearState(void) {
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// Return the pin to input mode, set pullup resistor
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cli();
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// Return the pin to input mode
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// cli();
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DDRB &= ~SERIAL_DATA_PIN;
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PORTB |= SERIAL_DATA_PIN;
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sei();
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// PORTB &= ~SERIAL_DATA_PIN;
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// sei();
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serialState = SERIAL_DISABLED;
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serialBitNum = 0;
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address = 0;
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@ -223,10 +235,8 @@ void handleSerClockInterrupt(void) {
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/*
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* For 20-byte PRAM equivalent commands, compute the actual PRAM
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* address by modifying the `address` variable in-place. Note that
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* `address` must have been already modified to remove the excess
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* bits. A status code is returned for commands that need special
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* processing:
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* address by modifying the `address` variable in-place. A status
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* code is returned for commands that need special processing:
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*
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* INVALID_CMD: Invalid command byte.
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* SECONDS_CMD: Special command: read seconds.
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@ -235,6 +245,9 @@ void handleSerClockInterrupt(void) {
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* SUCCESS_ADDR: Successful address computation.
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*/
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uint8_t decodePramCmd(boolean writeRequest) {
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// Discard the first bit and the last two bits, it's not pertinent
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// to command interpretation.
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address = (address&~(1<<7))>>2;
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if (address < 8) {
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// Little endian clock data byte
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return SECONDS_CMD;
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@ -301,9 +314,6 @@ void loop(void) {
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break;
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} else {
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boolean finished = false;
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// Discard the first bit and the last two bits, it's not
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// pertinent to command interpretation.
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address = (address&~(1<<7))>>2;
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// Decode the command/address.
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switch (decodePramCmd(writeRequest)) {
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case SECONDS_CMD:
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@ -331,7 +341,7 @@ void loop(void) {
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serialState = SENDING_DATA;
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serialBitNum = 0;
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// Set the pin to output mode
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DDRB |= SERIAL_DATA_PIN;
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configOutputOD(SERIAL_DATA_PIN);
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break;
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case RECEIVING_DATA:
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@ -340,9 +350,6 @@ void loop(void) {
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if (serialBitNum <= 7)
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break;
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// Discard the first bit and the last two bits, it's not
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// pertinent to command interpretation.
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address = (address&~(1<<7))>>2;
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// Decode the command/address.
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switch (decodePramCmd(writeRequest)) {
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case SECONDS_CMD:
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@ -374,7 +381,7 @@ void loop(void) {
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break;
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case SENDING_DATA:
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digitalWritePB(SERIAL_DATA_PIN, bitRead(serialData, 7 - serialBitNum));
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digitalWriteOD(SERIAL_DATA_PIN, bitRead(serialData, 7 - serialBitNum));
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serialBitNum++;
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/* if (serialBitNum <= 7)
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break; */
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@ -408,7 +415,7 @@ void loop(void) {
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serialState = SENDING_DATA;
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serialBitNum = 0;
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// Set the pin to output mode
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DDRB |= SERIAL_DATA_PIN;
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configOutputOD(SERIAL_DATA_PIN);
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break;
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case RECEIVING_XCMD_DATA:
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