Good Morning,
We have an ongoing challenge relating to the reliability of successfully receiving data from TPMS sensors containing the above RF transmitters. We are using a C1101 connected via SPI to an STM32 micro. We have been trying to resolve this (on and off) for about a year, this is the last ditch attempt to fix the issue before we start looking to using something other than the CC1101, I really hope somebody can spot something we have missed..
The TPMS sensors transmit at regular intervals (either every 30 or 60 seconds), they also have mode where they transmit an number of times instantly if rapid deflation occurs.
Our problem is that we are not able to successfully interpret data from the sensors reliably for every transmission, randomly, we will get a successful packet through every so often this could be every 30 secs, minute, 2 minutes, 3 minutes and so on. We are seeing good RSSI, anything from -50dbm to -75dbm.
Here is the protocol for the sensor.....
1 Communicate parameter
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CarrierCenterFrequency |
433.92MHz |
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Modulation |
Frequency Shift Keying (FSK) |
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Data Encoding |
Manchester (G.E. Thomas) Encoding |
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Baud Rate |
4.2 kbps ±5% |
2 Protocal format
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synchronization-head |
Frame start |
Frame Header |
ID1 |
ID2 |
ID3 |
ID4 |
Pressure |
Temperature |
Sensor Status |
REV |
Checksum |
end |
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0xFFFFFFFF |
0xF6 |
0xF0 |
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0x00 |
2.1 Frame Header:
Marks the start of data format，under this protocol frame header is 0xF0.
2.2 ID1, ID2, ID3，ID4
Transmitter ID (4 Bytes). See an example below.
01B2027F
2.3 Pressure: (in hexadecimal)
Formulas to convert actual pressure value:
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For sensor type 000 which means sensor pressure range 450Kpa（absolute
pressure），actual pressure value（relative pressure）formula is：
Tire pressure(in kPa)= value(in Decimal) *1.37
b) For sensor type 001 which means sensor pressure range 700Kpa（absolute pressure），actual pressure value（relative pressure）formula is：
Tire pressure(in kPa)= value(in Decimal) *2.35
c) For sensor type 010 which means sensor pressure range 1400Kpa（absolute pressure），actual pressure value（relative pressure）formula is：
Tire pressure(in kPa)= (value(in Decimal)-19)*5.5
d) For sensor type 011 which means sensor pressure range 2000Kpa（absolute pressure），actual pressure value（relative pressure）formula is：
Tire pressure(in kPa)= value(in Decimal) *8
（Note: 1 kPa = 0.145Psi ，sensor type refers to 3.5 Sensor Status Register bit6-bit4）
2.4 Temperature: (in hexadecimal)
Formulas to convert actual temperature value:
Tire temperature (in ℃)=value(in Decimal)-50
(Note: Conversion between ℉ and ℃：F=9/5*C+32)
2.5 Sensor Status Register:
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Bit 7 |
Bit 6 |
Bit 5 |
Bit 4 |
Bit 3 |
Bit 2 |
Bit 1 |
Bit 0 |
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0=awake; 1=normal （Just for commercial sensor） |
0 = no leakage 1 = leakage
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Rev |
Battery volume： 00=V<2.2V 01=2.6V>V≥2.2V 10=3V>V≥2.6V 11=V≥3V |
Sensor type： 00=450kpa 01=700kpa 10=1400kpa Else=REV |
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(Note：Sensor just transmit the value of pressure and temperature. You can decide the warning value in your receiver. We suggest that receiver will give warning when pressure turns out either 20% lower or 30% higher than standard pressure. In this case the standard pressure is set as 6bar, so the receiver will give high pressure warning if pressure is higher than 7.8bar, and give low pressure warning if pressure is lower than 4.8bar. Receiver will give high temperature warning if temperature is higher than 80℃.)
2.6 Checksum:
Checksum=ID1+ID2+ID3+ID4+Pressure_Status+Rev+1
Back in the distant past it was decided that a change to this protocol was required to have it work successfully with the CC1101, here are the details:
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Synchronization Header
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Frame
Start
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Frame Header
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Frame Data
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CRC checksum
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Frame End
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0xFFFFFFFF
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0xF6
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0x00
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Synchronization Header
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Frame
Start
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Length
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Frame Header
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Frame Data
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CRC checksum
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Frame End
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0xFFFFFF
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0xF6
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0x0A
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0x00
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2. FrameRegularReport
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Frame Header
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Frame Data
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Checksum
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0xF0
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ID1
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ID2
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ID3
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ID4
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Pressure
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Temperature
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Sensorstatus
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Reserve
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Checksum
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These are the Register settings for the CC1101 we are using (although other variations have been tried)
static const u8_t cc1101_valor_registers[] = {
// CC1101_IOCFG2 0x00 GDO2 Output Pin Configuration
0x0E, // Carrier Sense
// CC1101_IOCFG1 0x00 GDO1 Output Pin Configuration
0x2E, // tri-state high impedence
// CC1101_IOCFG0 0x00 GDO0 Output Pin Configuration
0x06, // Asserts when sync word has been sent / received, and de-asserts at the end of the packet.
// In RX, the pin will also de- assert when a packet is discarded due to address or maximum
// length filtering or when the radio enters RXFIFO_OVERFLOW state.
// In TX the pin will de-assert if the TX FIFO underflows.
// CC1101_FIFOTHR 0x03 RX FIFO and TX FIFO Thresholds
0x40 /* ADC retention */ | 0x01, /* tx fifo threshold of 57, rx fifo threshold of 8 */
// CC1101_SYNC1 0x04 Sync Word, High Byte
0xF6, // XX sync-word
// CC1101_SYNC0 0x05 Sync Word, Low Byte
// 0xF6, // TPMS sync-word
0x0A, // PMS sync-word
// CC1101_PKTLEN 0x06 Packet Length
// 0x0C, // TPMS packet length - NOTE - THIS IS IGNORED IN INFITIE PACKET LENGTH MODE
0x0A, // TPMS packet length - NOTE - THIS IS IGNORED IN INFITIE PACKET LENGTH MODE
// CC1101_PKTCTRL1 0x07 Packet Automation Control
0x04, // CRC autoflush disabled, append 2-byte RSSI/CRC status, no address check
// CC1101_PKTCTRL0 0x08 Packet Automation Control
// 0x02, /* data whitening off, use FIFOs, disable CRC, infinite packet length mode */
// 6 - WHITE_DATA
// 5:4 - PKT_FORMAT Format of RX and TX data
// 00 - Normal mode, use FIFOs for RX and TX
// 01 - Synchronous serial mode, Data in on GDO0 and data out on either of the GDOx pins
// 10 - Random TX mode; sends random data using PN9 generator. Used for test. Works as normal mode, setting 0 (00), in RX
// 11 - Asynchronous serial mode, Data in on GDO0 and data out on either of the GDOx pins
// 2 - CRC_EN
// 1:0 - LENGTH_CONFIG
// 00 - Fixed packet length mode. Length configured in PKTLEN register
// 01 - Variable packet length mode. Packet length configured by the first byte after sync word
// 10 - Infinite packet length mode
0x00, // fixed
// CC1101_ADDR 0x09 Device Address
0x00, /* broadcast address */
// CC1101_CHANNR 0x0A Channel Number
0x00, // channel number
// CC1101_FSCTRL1 0x0B Frequency Synthesizer Control
0x10, // intermediate frequency = 26000000/2^10 * 0x10 = 26000000/1024 * 0x10 = 406.250 kHz
// CC1101_FSCTRL0 0x0C Frequency Synthesizer Control
0x00, // frequency offset
// CC1101_FREQ2 0x0D Frequency Control Word, High Byte
// CC1101_FREQ1 0x0E Frequency Control Word, Middle Byte
// CC1101_FREQ0 0x0F Frequency Control Word, Low Byte
// carrier frequency = 26000000/2^16 * FREQ = 26000000/65536 * 0x10B071
// = 26000000/65536 * 1093745 = 433.919830 MHz (valor is 433.92)
0x10, 0xB0, 0x71,
// CC1101_MDMCFG4 0x10 Modem Configuration
// 7:6 - CHANBW_E
// 5:4 - CHANBW_M
// 3:0 - DRATE_E
// 0x98, // 162 kHz channel filter bandwidth
0x88, // 203 kHz channel filter bandwidth
// 0xF8, // 58 kHz channel filter bandwidth
// 0x08, // 812 kHz channel filter bandwidth
// 0xC8, // 102 kHz channel filter bandwidth
// CC1101_MDMCFG3 0x11 Modem Configuration
// 7:0 - DRATE_M - also has a 9th bit always set to 1
// 0x85,
0x83,
// CC1101_MDMCFG2 0x12 Modem Configuration
// 7 - DEM_DCFILT_OFF = Disable digital DC blocking filter before demodulator
// 6:4 - modulation format
// 0 - 2-FSK
// 1 - GFSK
// 3 - ASK/OOK
// 4 - 4-FSK
// 7 - MSK
// 3 - Enables Manchester encoding/decoding.
// 2:0 - Sync mode
// 0 - no preamble/sync
// 1 - 15/16 sync word bits detected
// 2 - 16/16 sync word bits detected
// 3 - 30/32 sync word bits detected
// 4 - no preamble/sync, carrier-sense above threshold
// 5 - 15/16 sync word bits detected + carrier-sense above threshold
// 6 - 16/16 sync word bits detected + carrier-sense above threshold
// 7 - 30/32 sync word bits detected + carrier-sense above threshold
0x0A, // manchester coding enabled, 16/16 sync word bits detected
// 0x09, // manchester coding enabled, 15/16 sync word bits detected
// CC1101_MDMCFG1 0x13 Modem Configuration
// 7 - Enable Forward Error Correction (FEC) with interleaving for packet payload
// 6:4 - minimum number of preable bytes
// 0 - 2 preamble bytes
// 1 - 3 preamble bytes
// 2 - 4 preamble bytes
// 3 - 6 preamble bytes
// 4 - 8 preamble bytes
// 5 - 12 preamble bytes
// 6 - 16 preamble bytes
// 7 - 24 preamble bytes
// 1:0 - CHANSPC_E - 2-bit exponent of channel spacing
0x22, // 4 byte preamble, CHANSPC_E = 2
// CC1101_MDMCFG0 0x14 Modem Configuration
// 7:0 - CHANSPC_M
// channel spacing = 26000000 / 2^18 * (256 + CHANSPC_M) * 2^CHANSPC_E
// = 26000000 / 262144 * 504 * 4 = 199.951172 kHz
0xF8,
// CC1101_DEVIATN 0x15 Modem Deviation Setting - 2-FSK, GFSK, 4-FSK only
// 6:4 - DEVIATION_E
// 2:0 - DEVIATION_M
// frequency deviation = 26000000 / 2^17 * (8 + DEVIATION_M) * 2^DEVIATION_E
// = 26000000 / 131072 * 15 * 16 = 47.607422 kHz
0x47,
// CC1101_MCSM2 0x16 Main Radio Control State Machine Configuration
// 4 - RX_TIME_RSSI - Direct RX termination based on RSSI measurement (carrier sense)
// 3- RX_TIME_QUAL - When the RX_TIME timer expires, the chip checks if sync word is found when RX_TIME_QUAL=0, or either sync word is found or PQI is set when RX_TIME_QUAL=1.
// 2:0 - RX_TIME - Timeout for sync word search in RX for both WOR mode and normal RX operation. The timeout is relative to the programmed EVENT0 timeout.
0x07, // RX_TIME = until end of packet
// CC1101_MCSM1 0x17 Main Radio Control State Machine Configuration
// 5:4 - CCA_MODE
// 00 - always
// 01 - if RSSI below threshold
// 10 - unless currently receiving a packet
// 11 - if RSSI below threshold unless currently receiving a packet
// 3:2 - RXOFF_MODE Select what should happen when a packet has been received
// 00 - IDLE
// 01 - FSTXON
// 10 - TX
// 11 - Stay in RX
// 1:0 - TXOFF_MODE Select what should happen when a packet has been sent (TX)
// 00 - IDLE
// 01 - FSTXON
// 10 - Stay in TX (start sending preamble)
// 11 - RX
0x30, // CCA_MODE - if RRSI below threshold unless currently receiving a packet
// CC1101_MCSM0 0x18 Main Radio Control State Machine Configuration
// 5:4 - FS_AUTOCAL Automatically calibrate when going to RX or TX, or back to IDLE
// 00 - Never
// 01 - When going from IDLE to RX or TX (or FSTXON)
// 10 - When going from RX or TX back to IDLE automatically
// 11 - Every 4th time when going from RX or TX to IDLE automatically
// 3:2 PO_TIMEOUT Programs the number of times the six-bit ripple counter must expire after XOSC has stabilized before CHP_RDYn goes low.
// 00 - 1 count - approx 2.3-2.4 us
// 01 - 16 counts - approx 37-39 us
// 10 - 64 counts - approx 149-155 us
// 11 - 256 counts - approx 597-620 us
// 1 PIN_CTRL_EN Enables the pin radio control option
// 0 XOSC_FORCE_ON Force the XOSC to stay on in the SLEEP state
0x18, // PO_TIMEOUT = 64 counts, auto calibrate when going from IDLE to RX or TX (or FSTXON)
// CC1101_FOCCFG 0x19 Frequency Offset Compensation Configuration
// 5 - FOC_BS_CS_GATE If set, the demodulator freezes the frequency offset compensation and clock recovery feedback loops until the CS signal goes high.
// 4:3 - FOC_PRE_K The frequency compensation loop gain to be used before a sync word is detected.
// 00 - K
// 01 - 2K
// 10 - 3K
// 11 - 4K
// 2 - FOC_POST_K The frequency compensation loop gain to be used after a sync word is detected
// 0 - Same as FOC_PRE_K
// 1 - K/2
// 1:0 - FOC_LIMIT The saturation point for the frequency offset compensation algorithm
// 00 - 0
// 01 - BW/8
// 10 - BW/4
// 11 - BW/2
// 0x76, // 3K, K/2, BW/4 - *** ORIGINAL - BAD ***
0x36, // 3K, Same as FOC_PRE_K, BW/4 - *** GOOD ***
// 0x1A, // 4K, Same as FOC_PRE_K, BW/4 - *** ? ***
// CC1101_BSCFG 0x1A Bit Synchronization Configuration
// 0x6D,
0x62,
// CC1101_AGCCTRL2 0x1B AGC Control
0x03, // target amplitude: 33dB - Maximum possible LNA + LNA 2 gain - All gain settings can be used
// CC1101_AGCCTRL1 0x1C AGC Control
0x40, // LNA gain decreased first
// CC1101_AGCCTRL0 0x1D AGC Control
0x91, // Medium hysterisis - Filter Samples: 16 - Normal AGC operation
// CC1101_WOREVT1 0x1E High Byte Event0 Timeout
0x87,
// CC1101_WOREVT0 0x1F Low Byte Event0 Timeout
0x6B,
// CC1101_WORCTRL 0x20 Wake On Radio Control
0xF8,
// CC1101_FREND1 0x21 Front End RX Configuration
0x56,
// CC1101_FREND0 0x22 Front End TX Configuration
// 2:0 - PA_POWER - Selects PA power setting. This value is an index to the PATABLE, which can be programmed with up to 8 different PA settings.
0x10,
// CC1101_FSCAL3 0x23 Frequency Synthesizer Calibration
0x99,
// CC1101_FSCAL2 0x24 Frequency Synthesizer Calibration
0x0A,
// CC1101_FSCAL1 0x25 Frequency Synthesizer Calibration
0x20,
// CC1101_FSCAL0 0x26 Frequency Synthesizer Calibration
0x0D,
// CC1101_RCCTRL1 0x27 RC Oscillator Configuration
0x27,
// CC1101_RCCTRL0 0x28 RC Oscillator Configuration
0x28
};
#endif // _CC1101_AXSCEND_VALOR_REGISTERS_H
