DIY-Multiprotocol-TX-Module/Multiprotocol/SFHSS_cc2500.ino

/*
 This project is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.

 Multiprotocol is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with Multiprotocol.  If not, see <http://www.gnu.org/licenses/>.
 */
// Last sync with main deviation/sfhss_cc2500.c dated 2016-03-23

#if defined(SFHSS_CC2500_INO)

#include "iface_cc2500.h"

#define SFHSS_COARSE	0

#define SFHSS_PACKET_LEN 13
#define SFHSS_TX_ID_LEN   2

uint8_t	fhss_code=0; // 0-27

enum {
    SFHSS_START = 0x00,
    SFHSS_CAL   = 0x01,
    SFHSS_DATA1 = 0x02,
    SFHSS_DATA2 = 0x03,
    SFHSS_TUNE  = 0x04
};

#define SFHSS_FREQ0_VAL 0xC4

// Some important initialization parameters, all others are either default,
// or not important in the context of transmitter
// IOCFG2   2F - GDO2_INV=0 GDO2_CFG=2F - HW0
// IOCFG1   2E - GDO1_INV=0 GDO1_CFG=2E - High Impedance
// IOCFG0   2F - GDO0 same as GDO2, TEMP_SENSOR_ENABLE=off
// FIFOTHR  07 - 33 decimal TX threshold
// SYNC1    D3
// SYNC0    91
// PKTLEN   0D - Packet length, 0D bytes
// PKTCTRL1 04 - APPEND_STATUS on, all other are receive parameters - irrelevant
// PKTCTRL0 0C - No whitening, use FIFO, CC2400 compatibility on, use CRC, fixed packet length
// ADDR     29
// CHANNR   10
// FSCTRL1  06 - IF 152343.75Hz, see page 65
// FSCTRL0  00 - zero freq offset
// FREQ2    5C - synthesizer frequency 2399999633Hz for 26MHz crystal, ibid
// FREQ1    4E
// FREQ0    C4
// MDMCFG4  7C - CHANBW_E - 01, CHANBW_M - 03, DRATE_E - 0C. Filter bandwidth = 232142Hz
// MDMCFG3  43 - DRATE_M - 43. Data rate = 128143bps
// MDMCFG2  83 - disable DC blocking, 2-FSK, no Manchester code, 15/16 sync bits detected (irrelevant for TX)
// MDMCFG1  23 - no FEC, 4 preamble bytes, CHANSPC_E - 03
// MDMCFG0  3B - CHANSPC_M - 3B. Channel spacing = 249938Hz (each 6th channel used, resulting in spacing of 1499628Hz)
// DEVIATN  44 - DEVIATION_E - 04, DEVIATION_M - 04. Deviation = 38085.9Hz
// MCSM2    07 - receive parameters, default, irrelevant
// MCSM1    0C - no CCA (transmit always), when packet received stay in RX, when sent go to IDLE
// MCSM0    08 - no autocalibration, PO_TIMEOUT - 64, no pin radio control, no forcing XTAL to stay in SLEEP
// FOCCFG   1D - not interesting, Frequency Offset Compensation
// FREND0   10 - PA_POWER = 0
const PROGMEM uint8_t SFHSS_init_values[] = {
  /* 00 */ 0x2F, 0x2E, 0x2F, 0x07, 0xD3, 0x91, 0x0D, 0x04,
  /* 08 */ 0x0C, 0x29, 0x10, 0x06, 0x00, 0x5C, 0x4E, SFHSS_FREQ0_VAL + SFHSS_COARSE,
  /* 10 */ 0x7C, 0x43, 0x83, 0x23, 0x3B, 0x44, 0x07, 0x0C,
  /* 18 */ 0x08, 0x1D, 0x1C, 0x43, 0x40, 0x91, 0x57, 0x6B,
  /* 20 */ 0xF8, 0xB6, 0x10, 0xEA, 0x0A, 0x11, 0x11
};

static void __attribute__((unused)) SFHSS_rf_init()
{
	CC2500_Strobe(CC2500_SIDLE);

	for (uint8_t i = 0; i < 39; ++i)
		CC2500_WriteReg(i, pgm_read_byte_near(&SFHSS_init_values[i]));

	prev_option = option;
	CC2500_WriteReg(CC2500_0C_FSCTRL0, option);
	
	CC2500_SetTxRxMode(TX_EN);
	CC2500_SetPower();
}

static void __attribute__((unused)) SFHSS_tune_chan()
{
	CC2500_Strobe(CC2500_SIDLE);
	CC2500_WriteReg(CC2500_0A_CHANNR, rf_ch_num*6+16);
	CC2500_Strobe(CC2500_SCAL);
}

static void __attribute__((unused)) SFHSS_tune_chan_fast()
{
	CC2500_Strobe(CC2500_SIDLE);
	CC2500_WriteReg(CC2500_0A_CHANNR, rf_ch_num*6+16);
	CC2500_WriteReg(CC2500_25_FSCAL1, calData[rf_ch_num]);
}

static void __attribute__((unused)) SFHSS_tune_freq()
{
	if ( prev_option != option )
	{
		CC2500_WriteReg(CC2500_0C_FSCTRL0, option);
		CC2500_WriteReg(CC2500_0F_FREQ0, SFHSS_FREQ0_VAL + SFHSS_COARSE);
		prev_option = option ;
		phase = SFHSS_START;	// Restart the tune process if option is changed to get good tuned values
	}
}

static void __attribute__((unused)) SFHSS_calc_next_chan()
{
    rf_ch_num += fhss_code + 2;
    if (rf_ch_num > 29)
	{
        if (rf_ch_num < 31)
			rf_ch_num += fhss_code + 2;
        rf_ch_num -= 31;
    }
}

// Channel values are 12-bit values between 1020 and 2020, 1520 is the middle.
// Futaba @140% is 2070...1520...970
// Values grow down and to the right.
static void __attribute__((unused)) SFHSS_build_data_packet()
{
	uint16_t ch[4];
	// command.bit0 is the packet number indicator: =0 -> SFHSS_DATA1, =1 -> SFHSS_DATA2
	// command.bit1 is unknown but seems to be linked to the payload[0].bit0 but more dumps are needed: payload[0]=0x82 -> =0, payload[0]=0x81 -> =1
	// command.bit2 is the failsafe transmission indicator: =0 -> normal data, =1->failsafe data
	// command.bit3 is the channels indicator: =0 -> CH1-4, =1 -> CH5-8
	
	//Coding below matches the Futaba T8J transmission scheme DATA1->CH1-4, DATA2->CH5-8, DATA1->CH5-8, DATA2->CH1-4,...
	// XK, T10J and TM-FH are different with a classic DATA1->CH1-4, DATA2->CH5-8,...
	//Failsafe is sent twice every couple of seconds (unknown but >5s) 
	
	uint8_t command= (phase == SFHSS_DATA1) ? 0 : 1;	// Building packet for Data1 or Data2
	counter+=command;
	#ifdef FAILSAFE_ENABLE
		if( (counter&0x3FC) == 0x3FC && IS_FAILSAFE_VALUES_on)
		{	// Transmit failsafe data twice every 7s
			if( ((counter&1)^(command&1)) == 0 )
				command|=0x04;							// Failsafe
		}
		else
	#endif
			command|=0x02;								// Assuming packet[0] == 0x81
	counter&=0x3FF;										// Reset failsafe counter
	if(counter&1) command|=0x08;						// Transmit lower and upper channels twice in a row

	uint8_t ch_offset = (command&0x08) >> 1;			// CH1..CH4 or CH5..CH8

	#ifdef FAILSAFE_ENABLE
		if(command&0x04)
		{	//Failsafe data are:
			// 0 to 1023 -> no output on channel
			// 1024-2047 -> hold output on channel
			// 2048-4095 -> channel_output=(data&0x3FF)*5/4+880 in µs
			// Notes:
			//    2048-2559 -> does not look valid since it only covers the range from 1520µs to 2160µs 
			//    2560-3583 -> valid for any channel values from 880µs to 2160µs
			//    3584-4095 -> looks to be used for the throttle channel with values ranging from 880µs to 1520µs
			for(uint8_t i=0;i<4;i++)
			{
				ch[i]=Failsafe_data[CH_AETR[ch_offset+i]];
				if(ch[i]==FAILSAFE_CHANNEL_HOLD)
					ch[i]=1024;
				else if(ch[i]==FAILSAFE_CHANNEL_NOPULSES)
					ch[i]=0;
				else
				{ //Use channel value
					ch[i]=(ch[i]>>1)+2560;
					if(CH_AETR[ch_offset+i]==THROTTLE && ch[i]<3072)		// Throttle
						ch[i]+=1024;
				}
			}
		}
		else
	#endif
		{	//Normal data
			for(uint8_t i=0;i<4;i++)
				ch[i] = convert_channel_16b_nolimit(CH_AETR[ch_offset+i],2020,1020);
		}

	
	// XK		[0]=0x81 [3]=0x00 [4]=0x00
	// T8J		[0]=0x81 [3]=0x42 [4]=0x07
	// T10J		[0]=0x81 [3]=0x0F [4]=0x09
	// TM-FH	[0]=0x82 [3]=0x9A [4]=0x06
	packet[0] = 0x81;	// can be 80 or 81 for Orange, only 81 for XK
	packet[1] = rx_tx_addr[0];
	packet[2] = rx_tx_addr[1];
	packet[3] = 0x00;	// unknown but prevents some receivers to bind if not 0
	packet[4] = 0x00;	// unknown but prevents some receivers to bind if not 0
	packet[5] = (rf_ch_num << 3) | ((ch[0] >> 9) & 0x07);
	packet[6] = (ch[0] >> 1);
	packet[7] = (ch[0] << 7) | ((ch[1] >> 5) & 0x7F );
	packet[8] = (ch[1] << 3) | ((ch[2] >> 9) & 0x07 );
	packet[9] = (ch[2] >> 1);
	packet[10] = (ch[2] << 7) | ((ch[3] >> 5) & 0x7F );
	packet[11] = (ch[3] << 3) | ((fhss_code >> 2) & 0x07 );
	packet[12] = (fhss_code << 6) | command;
}

static void __attribute__((unused)) SFHSS_send_packet()
{
    CC2500_WriteData(packet, SFHSS_PACKET_LEN);
}

uint16_t ReadSFHSS()
{
	switch(phase)
	{
		case SFHSS_START:
			rf_ch_num = 0;
			SFHSS_tune_chan();
			phase = SFHSS_CAL;
			return 2000;
		case SFHSS_CAL:
			calData[rf_ch_num]=CC2500_ReadReg(CC2500_25_FSCAL1);
			if (++rf_ch_num < 30)
				SFHSS_tune_chan();
			else
			{
				rf_ch_num = 0;
				counter = 0;
				phase = SFHSS_DATA1;
			}
			return 2000;

		/* Work cycle: 6.8ms */
#define SFHSS_PACKET_PERIOD	6800
#define SFHSS_DATA2_TIMING	1625	// Adjust this value between 1600 and 1650 if your RX(s) are not operating properly
		case SFHSS_DATA1:
			SFHSS_build_data_packet();
			SFHSS_send_packet();
			phase = SFHSS_DATA2;
			return SFHSS_DATA2_TIMING;								// original 1650
		case SFHSS_DATA2:
			SFHSS_build_data_packet();
			SFHSS_send_packet();
			SFHSS_calc_next_chan();
			phase = SFHSS_TUNE;
			return (SFHSS_PACKET_PERIOD -2000 -SFHSS_DATA2_TIMING);	// original 2000
		case SFHSS_TUNE:
			phase = SFHSS_DATA1;
			SFHSS_tune_freq();
			SFHSS_tune_chan_fast();
			CC2500_SetPower();
			return 2000;											// original 3150
	}
	return 0;
}

// Generate internal id
static void __attribute__((unused)) SFHSS_get_tx_id()
{
	// Some receivers (Orange) behaves better if they tuned to id that has
	//  no more than 6 consecutive zeros and ones
	uint32_t fixed_id;
	uint8_t run_count = 0;
	// add guard for bit count
	fixed_id = 1 ^ (MProtocol_id & 1);
	for (uint8_t i = 0; i < 16; ++i)
	{
		fixed_id = (fixed_id << 1) | (MProtocol_id & 1);
		MProtocol_id >>= 1;
		// If two LS bits are the same
		if ((fixed_id & 3) == 0 || (fixed_id & 3) == 3)
		{
			if (++run_count > 6)
			{
				fixed_id ^= 1;
				run_count = 0;
			}
		}
		else
			run_count = 0;
	}
	//    fixed_id = 0xBC11;
	rx_tx_addr[0] = fixed_id >> 8;
	rx_tx_addr[1] = fixed_id >> 0;
}

uint16_t initSFHSS()
{
	BIND_DONE;	// Not a TX bind protocol
	SFHSS_get_tx_id();

	fhss_code=random(0xfefefefe)%28; // Initialize it to random 0-27 inclusive

	SFHSS_rf_init();
	phase = SFHSS_START;
	return 10000;
}

#endif