Remove unnecessary pull-ups on inputs, open-drain output.

This commit is contained in:
Andrew Makousky 2020-09-05 15:37:02 -05:00
parent 652aab70ab
commit e2483ddd59

View File

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