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4 byte Bus id implementation - router functionality
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@gioblu
gioblu committed May 24, 2016
1 parent 7fa3187 commit 512f290
Showing 1 changed file with 99 additions and 28 deletions.
127 changes: 99 additions & 28 deletions PJON.h
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Expand Up @@ -44,6 +44,13 @@ limitations under the License. */
#define NAK 21
#define NOT_ASSIGNED 255

/* A bus id is an array of 4 bytes containing a unique set.
The default setting is to run a local bus (0.0.0.0), in this
particular case the obvious bus id is omitted from the packet
content to reduce overhead. */

uint8_t localhost[4] = {0, 0, 0, 0};

/* Internal constants */
#define FAIL 0x100
#define TO_BE_SENT 74
Expand Down Expand Up @@ -72,7 +79,7 @@ limitations under the License. */
/* Maximum id scan time (5 seconds) */
#define MAX_ID_SCAN_TIME 5000000

struct packet {
struct Packet {
uint8_t attempts;
uint8_t device_id;
char *content;
Expand All @@ -82,11 +89,11 @@ limitations under the License. */
uint32_t timing;
};

typedef void (* receiver)(uint8_t length, uint8_t *payload);
typedef void (* receiver)(uint8_t id, uint8_t *payload, uint8_t length);
typedef void (* error)(uint8_t code, uint8_t data);

static void dummy_receiver_handler(uint8_t id, uint8_t *payload, uint8_t length) {};
static void dummy_error_handler(uint8_t code, uint8_t data) {};
static void dummy_receiver_handler(uint8_t length, uint8_t *payload) {};

template<typename Strategy = SoftwareBitBang>
class PJON {
Expand All @@ -95,14 +102,38 @@ limitations under the License. */

public:

/* PJON default initialization:
Acknowledge: true
Bus id: 0.0.0.0
device id: NOT_ASSIGNED (255)
Mode: HALF_DUPLEX
Strategy: SoftwareBitBang */

PJON() : strategy(Strategy()) {
_device_id = NOT_ASSIGNED;
this->set_default();
set_default();
};

PJON(uint8_t id) : strategy(Strategy()) {
_device_id = id;
this->set_default();

/* PJON initialization passing device id:
PJON bus(1); */

PJON(uint8_t device_id) : strategy(Strategy()) {
_device_id = device_id;
set_default();
};


/* PJON initialization passing bus and device id:
uint8_t my_bus = {1, 1, 1, 1};
PJON bus(my_bys, 1); */

PJON(const uint8_t *b_id, uint8_t device_id) : strategy(Strategy()) {
for(uint8_t i = 0; i < 4; i++)
bus_id[i] = b_id[i];

_device_id = device_id;
set_default();
};


Expand Down Expand Up @@ -135,6 +166,16 @@ limitations under the License. */
};


/* Check equality between two bus ids */

boolean bus_id_equality(uint8_t *name_one, uint8_t *name_two) {
for(uint8_t i = 0; i < 4; i++)
if(name_one[i] != name_two[i])
return false;
return true;
};


/* Compute CRC8 with a table-less implementation: */

uint8_t compute_crc_8(char input_byte, uint8_t crc) {
Expand Down Expand Up @@ -165,24 +206,34 @@ limitations under the License. */
data[i] = state = Strategy::receive_byte(_input_pin, _output_pin);
if(state == FAIL) return FAIL;

if(i == 0 && data[i] != _device_id && data[i] != BROADCAST)
if(i == 0 && data[i] != _device_id && data[i] != BROADCAST && !_router)
return BUSY;

/* If an id is assigned to this bus it means that is potentially
sharing its medium, or the device could be connected in parallel
with other buses. Bus id equality is checked to avoid collision
i.e. id 1 bus 1, should not receive a message for id 1 bus 2. */

if(i == 1) {
if(data[i] > 3 && data[i] < PACKET_MAX_LENGTH)
package_length = data[i];
else return FAIL;
}

if(!_local && !_router && i > 1 && i < 6)
if(bus_id[i - 2] != data[i])
return BUSY;

CRC = compute_crc_8(data[i], CRC);
}
if(!CRC) {
if(data[0] != BROADCAST && _mode != SIMPLEX) {
if(_acknowledge && data[0] != BROADCAST && _mode != SIMPLEX) {
Strategy::send_response(ACK, _input_pin, _output_pin);
}
_receiver(data[1] - 3, data + 2);
_receiver(data[0], data + 2, data[1] - 3);
return ACK;
} else {
if(data[0] != BROADCAST && _negative_acknowledge && _mode != SIMPLEX) {
if(_acknowledge && data[0] != BROADCAST && _mode != SIMPLEX) {
Strategy::send_response(NAK, _input_pin, _output_pin);
}
return NAK;
Expand Down Expand Up @@ -276,7 +327,7 @@ limitations under the License. */
Channel analysis Transmission Response
_____ _____________________________ _____
| C-A | | ID | LENGTH | CONTENT | CRC | | ACK |
<--|-----|---------|----|--------|---------|-----|--> <----|-----|
<--|-----|---< >---|----|--------|---------|-----|--> <----|-----|
| 0 | | 12 | 4 | 64 | 130 | | 6 |
|_____| |____|________|_________|_____| |_____| */

Expand All @@ -285,11 +336,20 @@ limitations under the License. */
if(_mode != SIMPLEX && !Strategy::can_start(_input_pin, _output_pin)) return BUSY;

uint8_t CRC = 0;

Strategy::send_byte(id, _input_pin, _output_pin);
CRC = compute_crc_8(id, CRC);
Strategy::send_byte(length + 3, _input_pin, _output_pin);
CRC = compute_crc_8(length + 3, CRC);
Strategy::send_byte(length + ((_local) ? 3 : 7), _input_pin, _output_pin);
CRC = compute_crc_8(length + ((_local) ? 3 : 7), CRC);

/* If an id is assigned to the bus, the packet's content is prepended by
the ricipient's bus id. This opens up the possibility to have more than
one bus sharing the same medium. */

if(!_local)
for(uint8_t i = 0; i < 4; i++) {
Strategy::send_byte(bus_id[i], _input_pin, _output_pin);
CRC = compute_crc_8(bus_id[i], CRC);
}

for(uint8_t i = 0; i < length; i++) {
Strategy::send_byte(string[i], _input_pin, _output_pin);
Expand All @@ -298,7 +358,7 @@ limitations under the License. */

Strategy::send_byte(CRC, _input_pin, _output_pin);

if(id == BROADCAST || _mode == SIMPLEX) return ACK;
if(!_acknowledge || id == BROADCAST || _mode == SIMPLEX) return ACK;

uint16_t response = Strategy::receive_response(_input_pin, _output_pin);

Expand All @@ -314,11 +374,28 @@ limitations under the License. */
};


/* Configure sincronous acknowledge presence: */

void set_acknowledge(boolean state) {
_acknowledge = state;
};


/* Set communication mode: */

void set_communication_mode(uint8_t mode) {
_mode = mode;
};


/* Set bus state default configuration: */

void set_default() {
_mode = HALF_DUPLEX;
_negative_acknowledge = true;

if(!bus_id_equality(bus_id, localhost))
_local = false;

set_error(dummy_error_handler);
set_receiver(dummy_receiver_handler);

Expand Down Expand Up @@ -353,15 +430,6 @@ limitations under the License. */
};


/* Configure if to send or not NAK back to transmitter in case of error:
Sending NAK when error is detected can be critical in high interference
scenarios. (broken id reception) */

void set_negative_acknowledge(boolean state) {
_negative_acknowledge = state;
};


/* Set the communicaton pin: */

void set_pin(uint8_t pin) {
Expand Down Expand Up @@ -443,14 +511,17 @@ limitations under the License. */
};

uint8_t data[PACKET_MAX_LENGTH];
packet packets[MAX_PACKETS];
Packet packets[MAX_PACKETS];
uint8_t bus_id[4] = {0, 0, 0, 0};
private:
boolean _acknowledge = true;
uint8_t _device_id;
uint8_t _input_pin;
boolean _local = true;
uint8_t _mode;
uint8_t _output_pin;
receiver _receiver;
boolean _router = false;
error _error;
boolean _negative_acknowledge;
};
#endif

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