|
Engduino v2.1
|
This is the driver code for IR on the Engduino On v1.0 this is the Vishay TFBS4711 chip. More...
Files | |
| file | EngduinoIR.cpp |
Engduino IR driver. | |
| file | EngduinoIR.h |
Engduino IR driver. | |
Functions | |
| ISR (TIMER3_COMPB_vect) | |
| TIMER3 interrupt service routine, called when the timer has expired. | |
| ISR (TIMER1_COMPB_vect) | |
| TIMER1 interrupt service routine, called when the timer has expired. | |
| EngduinoIRClass::EngduinoIRClass () | |
| Constructor. | |
| void | EngduinoIRClass::begin () |
| begin function - must be called before using other functions | |
| void | EngduinoIRClass::end () |
| end function - switch off the IR | |
| void | EngduinoIRClass::sendBit (bool b) |
| Send a single bit. | |
| void | EngduinoIRClass::send (uint8_t b, bool startstop=true) |
| Send a byte. | |
| void | EngduinoIRClass::send (uint8_t *buf, unsigned int len, bool startstop=true) |
| Send a buffer of bytes. | |
| void | EngduinoIRClass::send (char *buf, unsigned int len, bool startstop=true) |
| Send a buffer of bytes. | |
| void | EngduinoIRClass::sendRaw (unsigned int *buf, int len) |
| Raw send function. | |
| int | EngduinoIRClass::recv (uint8_t *buf, uint16_t timeout=0, bool startstop=true) |
| Blocking receive of an IR transmission, with optional timeout. | |
| int | EngduinoIRClass::recvRaw (uint16_t *buf, uint16_t timeout=0) |
| Raw receive function - returns timings for inter-mark gaps. | |
This is the driver code for IR on the Engduino On v1.0 this is the Vishay TFBS4711 chip.
This driver makes use of a timer to measure the length of inter-mark gaps, and an edge-triggered ISR to know where the marks are.
Because the ISR for the LEDs occupies considerable time, this can run slowly and somewhat erratically, meaning that only a rather low data rate is possible. The code distinguishes between marks and spaces based on the relative timings of them, and the threshold is hardwired in the header file.
This code makes use of timer 3, which cannot then be used for other purposes.
| void EngduinoIRClass::begin | ( | ) |
begin function - must be called before using other functions
This function enables the IR, sets up the receive state machine, initialises timer 3 to run at 1MHz, to give high resolution timings, and sets the interrupts for the TFBS4711 IR device. The TFBS4711 chip will drive the IR_RX line low briefly when receiving a mark, and will not generate any event whilst receiving a space. Consequently, we can only tell the difference between them by looking at the gaps between two marks; longer gaps mean more spaces.
Definition at line 58 of file EngduinoIR.cpp.
| void EngduinoIRClass::end | ( | ) |
end function - switch off the IR
Switch off both the IR chip and the ISRs.
Definition at line 136 of file EngduinoIR.cpp.
| EngduinoIRClass::EngduinoIRClass | ( | ) |
| ISR | ( | TIMER3_COMPB_vect | ) |
TIMER3 interrupt service routine, called when the timer has expired.
TIMER3 interrupt code - timer 3 COMPB is used as a timeout to determine when a code we are receiving has ended, or when a call to the recv function has timed out.
Definition at line 349 of file EngduinoIR.cpp.
| ISR | ( | TIMER1_COMPB_vect | ) |
TIMER1 interrupt service routine, called when the timer has expired.
TIMER1 interrupt code - Set for an overflowed count driven by the T1 pin which is connected to IR_RX. Such events occur in 2.2us periods when there is a mark on the IR. The width of the pulse is unrelated to the baud rate of transmission, so we simply time the space between marks using timer 3, setting (and resetting) a timeout which, when it expires, indicates that the code has ended.
It is necessary for us to have marks come in pairs to drive this ISR correctly - the first mark counts from 0-1, generating an interrupt, the second resets the timer counter to 0.
Note: This approach is dictated by the connections on the board. It means that we cannot use a remote control with the Engduino v2 because that will not generate the marks in pairs as we have done above.
Definition at line 383 of file EngduinoIR.cpp.
| int EngduinoIRClass::recv | ( | uint8_t * | buf, |
| uint16_t | timeout = 0, |
||
| bool | startstop = true |
||
| ) |
Blocking receive of an IR transmission, with optional timeout.
| buf | The buffer in which to place the received data |
| timeout | The time to wait before returning |
| startstop | Whether to remove start/stop bits from transmission |
Receive a message if it's there to be received. Otherwise wait for a time that depends on the timeout value: if this is zero (as it is by default), then wait forever, else set a timer. If the timer expires return a negative number (-1), else return the length of the buffer received. The timeout is considered not to have expired if, by the time the period is passed, a message has *started* to arrive.
The first received bit is placed in the MSB, meaning that if there is not a complete byte's worth of data, the lowest bits will be zero.
Note: Differentiating between a mark and a space is based on a hardwired test of length.
Definition at line 449 of file EngduinoIR.cpp.
| int EngduinoIRClass::recvRaw | ( | uint16_t * | buf, |
| uint16_t | timeout = 0 |
||
| ) |
Raw receive function - returns timings for inter-mark gaps.
| buf | The buffer in which to place the inter-mark timings |
| timeout | The time to wait before returning |
Receive a message if it's there to be received. Otherwise wait for a time that depends on the timeout value: if this is zero (as it is by default), then wait forever, else set a timer. If the timer expires return a negative number (-1), else return the length of the buffer received. The timeout is considered not to have expired if, by the time the period is passed, a message has *started* to arrive.
On return, the buffer contains the timings, in microseconds, between pairs of marks. Again, this allows a higher-level protocol to be written in a sketch.
Definition at line 506 of file EngduinoIR.cpp.
| void EngduinoIRClass::send | ( | uint8_t | b, |
| bool | startstop = true |
||
| ) |
Send a byte.
| b | The byte to send |
| startstop | Whether to send mark bits as start/stop markers |
If startstop is true, send a mark at the beginning and end of data, but between the two, send the byte, LSB first.
Definition at line 190 of file EngduinoIR.cpp.
| void EngduinoIRClass::send | ( | uint8_t * | buf, |
| unsigned int | len, | ||
| bool | startstop = true |
||
| ) |
Send a buffer of bytes.
| buf | The buffer of bytes to send as a (uint8_t *) |
| len | Length of the buffer |
| startstop | Whether to send mark bits as start/stop markers |
If startstop is true, send a mark at the beginning and end of data, but between the two, send the individual bytes, LSB first.
Definition at line 227 of file EngduinoIR.cpp.
| void EngduinoIRClass::send | ( | char * | buf, |
| unsigned int | len, | ||
| bool | startstop = true |
||
| ) |
Send a buffer of bytes.
| buf | The buffer of bytes to send as a (char *) |
| len | Length of the buffer |
| startstop | Whether to send mark bits as start/stop markers |
If startstop is true, send a mark at the beginning and end of data, but between the two, send the individual bytes, LSB first.
Definition at line 260 of file EngduinoIR.cpp.
| void EngduinoIRClass::sendBit | ( | bool | b | ) |
Send a single bit.
| b | The boolean representing the bit to be sent. |
This sends a single bit. A double mark is sent as a mark signal, and a space is sent as a space followed by a double mark. The double mark is used because the input from the RX process goes to drive the counter in a timer. Even set to one count the counter expires and is reset only once every two marks - i.e. we get one receive interrupt every two marks. This encoding works well because we do not have to concern ourselves about the relative timings of runs of spaces. Instead a mark - space transition should always be a constant length, and this should be considerably longer than a mark - mark transition.
Definition at line 160 of file EngduinoIR.cpp.
| void EngduinoIRClass::sendRaw | ( | unsigned int * | buf, |
| int | len | ||
| ) |
Raw send function.
Provide timings for mark and space pairs
| buf | Buffer containing alternate mark/space timings in microseconds |
| len | Length of the buffer |
The argument to this function is a buffer containing alternate mark/space timings, given in milliseconds, allowing a higher-level protocol to be written in a sketch.
Definition at line 278 of file EngduinoIR.cpp.
1.7.6.1