arrow-firmware/components/kiss/kiss.c

/*
 * tnc_kiss.c
 *
 *  Created on: Feb 26, 2019
 *      Author: curiousmuch
 */

// basic set of functions at this moment which decodes KISS

#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/ringbuf.h"
#include "esp_log.h"
#include <stdio.h>
#include "kiss.h"

kiss_buffer_t rx_buffer;
kiss_buffer_t tx_buffer;
kiss_settings_t kiss_settings;

void static kiss_clear_tx_buffer(void)
{
	ESP_LOGD(TNC_TAG, "TNC buffer cleared.");
	tx_buffer.index = 0;
	tx_buffer.status = FRAME_INCOMPLETE;
}

void static kiss_append_tx_buffer(uint8_t chr)
{
	ESP_LOGD(TNC_TAG, "Appending %x to KISS TX buffer.", chr);
	// ERROR - Packet Buffer Overflow
	if (tx_buffer.index >= tx_buffer.max_len)
	{
		ESP_LOGE(TNC_TAG, "TNC TX buffer overflow");
		kiss_clear_tx_buffer();
	}
	tx_buffer.buf[(tx_buffer.index)] = chr;
	tx_buffer.index = tx_buffer.index + 1;
}

void kiss_transmit(uint8_t type, uint8_t *data, uint32_t len)
{
	uint32_t i;

	// TODO: Cancel TX to BLE TX Buffer if overflow is detected
	// TODO: Can we eliminate TX buffer and use BLE Buffer only?????

	kiss_clear_tx_buffer();
	kiss_append_tx_buffer(KISS_FEND);
	kiss_append_tx_buffer(type);

	// cycle
	for (i=0; i<(len); i++)
	{
		if (data[i] == KISS_FEND)
		{
			kiss_append_tx_buffer(KISS_FESC);
			kiss_append_tx_buffer(KISS_TFEND);
		}
		else if (data[i] == KISS_FESC)
		{
			kiss_append_tx_buffer(KISS_FESC);
			kiss_append_tx_buffer(KISS_TFESC);
		}
		else
		{
			kiss_append_tx_buffer(data[i]);
		}
	}

	kiss_append_tx_buffer(KISS_FEND);

	// activate callback function
	kiss_settings.tx_callback(tx_buffer.buf, tx_buffer.index);

}

void kiss_clear_buffer(void)
{
	ESP_LOGD(TNC_TAG, "TNC buffer cleared.");
	rx_buffer.index = 0;
}

void kiss_append_buffer(uint8_t chr)
{
	ESP_LOGD(TNC_TAG, "Appending %x to TNC buffer.", chr);
	// ERROR - Packet Buffer Overflow
	if (rx_buffer.index >= rx_buffer.max_len)
	{
		ESP_LOGE(TNC_TAG, "TNC buffer overflow");
		kiss_clear_buffer();
	}
	rx_buffer.buf[(rx_buffer.index)] = chr;
	rx_buffer.index = rx_buffer.index + 1;
}

//extern RingbufHandle_t radio_tx_buf;

// Frame Format
// [ Command Byte ][ Data ]
void kiss_process_frame(void)
{
	// minimum kiss frame is 2 bytes
    if (rx_buffer.index < 2)
    	return;

    uint8_t data_byte, tnc_number;

    data_byte = rx_buffer.buf[0];
    tnc_number = (data_byte >> 4) & 0x0F;

    // confirm packet is for this device
    if (tnc_number == kiss_settings.tnc_number)
    	kiss_settings.rx_callback(rx_buffer.buf, rx_buffer.index);

    kiss_clear_buffer();
}


// TNC needs the ability to RX KISS frame, decode it, schedule it, and then send out via APRS or Arrow-Net
// TNC needs the ability to switch to RX mode,

void kiss_init(uint8_t tnc_number, kiss_cb_t tx_cb, kiss_cb_t rx_cb)
{
	// TODO: make frame buffer dynamic
	rx_buffer.max_len = FRAME_BUFFER_SIZE;
	tx_buffer.max_len = FRAME_BUFFER_SIZE;

	// set tnc number
	kiss_settings.tnc_number = tnc_number;

	// set callback functions
	kiss_settings.rx_callback = rx_cb;
	kiss_settings.tx_callback = tx_cb;
}

// Decode KISS-TNC data from SPP Interface and combine until there is
// is a valid packet. Pass valid packet / frame to AX.25 engine.
// Data Flow:
// (1) SPP interface hands over data array which is runs a state machine to decode the KISS Frame
// (2) Decoded information is uploaded thrown into a buffer
// (3) When frame is complete the state machine will copy or indicate to another task to dump the buffer
// If the frame is not completed, the state machine will wait until more data is provided by the SPP interface.
// If the frame is corrupted or the buffer fills, the frame will be dumped and the error must be logged.
KISS_STATE_t kiss_state = FRAME_END;
void kiss_receive(uint8_t* data, uint16_t len)
{
	uint32_t i;
	uint8_t chr;
	for (i=0; i<len; i++)
	{
		chr = data[i];
		switch(kiss_state) {
			case ESC_MODE: {
				if (chr == KISS_TFEND)
				{
					kiss_append_buffer(KISS_FEND);		// append FEND to frame
					kiss_state = FRAME_ASS;				// return to assembly
				}
				else if (chr == KISS_TFESC)
				{
					kiss_append_buffer(KISS_FESC);		// append FESC to frame
					kiss_state = FRAME_ASS;				// return to assembly
				}
				else if (chr == KISS_FEND)
				{
					kiss_process_frame();				// process frame
					kiss_state = FRAME_END;				// end frame assembly
				}
				else
				{
					// log error
					kiss_append_buffer(chr);			// append chr to frame
					kiss_state = FRAME_ASS;				// return to assembly
				}
				break;
			}
			case FRAME_END: {
				if (chr != KISS_FEND)
				{
					kiss_append_buffer(chr);			// append chr to frame
					kiss_state = FRAME_ASS;				// return to assembly
				}
				else
				{
					kiss_state = FRAME_END;				// stay in frame end
				}
				break;
			}
			case FRAME_ASS: {
				if (chr == KISS_FESC)
				{
					kiss_state = ESC_MODE;
				}
				else if (chr == KISS_FEND)
				{
					kiss_process_frame();				// process frame
					kiss_state = FRAME_END;				// end frame assembly
				}
				else
				{
					kiss_append_buffer(chr);			// append chr to frame
					kiss_state = FRAME_ASS;				// continue frame assembly
				}
				break;
			default: {
				ESP_LOGE(TNC_TAG, "TNC FSM Error");
			}
			}
		}
	}
}