/*
* Maplin N96GY (Fine Offset WH1080/WH1081) RF receiver using a
* Raspberry Pi and an RFM01 or RFM12b transceiver module. I switched
* to an RFM01 module after frying the RFM12b; turns out it works *far*
* better anyway, so it was something of a blessing in disguise.
*
* The code here is really just experimental, and is not intended to be used
* beyond a learning excercise. It conveys the basics of what's required
* to get the Raspberry Pi receiving sensor data, but that's about it!
*
* I can't be sure it still works with an RFM12b, but it shouldn't be far off
* the mark if not - a bit of debugging may be required, but I no longer
* have a working module to test.
*
* This program configures an RFM01 to receive RF transmissions from the
* weather station's sensors, and reads them directly from the receiver's
* demodulator via the DATA pin, in to a GPIO pin on the Raspberry Pi. The
* pulse widths are used to derive the data-packet that was transmitted.
*
* The process switches to SCHED_RR for realtime latency while it waits
* for a packet. It returns to SCHED_OTHER when a packet is received.
* This ensures that bit transitions aren't missed, and also allows very
* heavy loads to run on the Pi while maintaining reliable reads. Optionally,
* the command 'sysctl kernel.sched_wakeup_granularity_ns=100000' may
* further improve latency, though it seems to work with Raspbian defaults
* regardless.
*
* Includes Luc Small's version of CRC8 from the OneWire Arduino library
* adapted for Fine Offset's calculations that also happen to work for this
* weather station. The SPI code was derived from the driver example at
* kernel.org.
*
* This program 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 as version 2 of the License.
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <unistd.h>
#include <stdint.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/spi/spidev.h>
#include <time.h>
#include <sched.h>
#include "wh1080_rf.h"
#include "bcm2835.h"
#include "rfm01.h"
#include "wunderground.h"
uint16_t bw_scale[6] = {BW_67, BW_134, BW_200, BW_270, BW_340, BW_400};
struct RSSI rssi_scale[24] = {
L0R73,L0R79,L0R85,L0R91,L0R97,L0R103,
L6R73,L6R79,L6R85,L6R91,L6R97,L6R103,
L14R73,L14R79,L14R85,L14R91,L14R97,L14R103,
L20R73,L20R79,L20R85,L20R91,L20R97,L20R103,
};
uint8_t _crc8( uint8_t *addr, uint8_t len);
static void pabort(const char *s)
{
perror(s);
abort();
}
static const char *device = "/dev/spidev0.0";
static uint8_t mode=0;
static uint8_t bits = 8;
static uint32_t speed = 1000000;
static uint16_t delay=0;
static uint16_t send_command16(int fd, uint16_t cmd)
{
uint8_t tx[2];
uint8_t *buf = (uint8_t *)&cmd;
tx[0] = buf[1];
tx[1] = buf[0];
//printf("SPI %02x%02x\n", buf[1], buf[0]);
uint8_t rx[2] = {0, 0};
struct spi_ioc_transfer tr = {
.tx_buf = (unsigned long)tx,
.rx_buf = (unsigned long)rx,
.len = 2,
.delay_usecs = delay,
.speed_hz = speed,
.bits_per_word = bits,
};
if(ioctl(fd, SPI_IOC_MESSAGE(1), &tr) < 1)
pabort("can't send spi message");
return (((uint16_t)rx[0]) << 8) + rx[1];
}
int g_low_threshold = 1000;
uint16_t cmd_reset = CMD_RESET;
uint16_t cmd_status = CMD_STATUS;
// Expected bit rate: 95 = 1959, 99 = 1700, 9c = 1500, a1 = 1268, aa = 1000, b8 - 756, d5 = 500
uint16_t cmd_drate = CMD_DRATE|0xaa; // drate is c8xx rather than c6xx
uint16_t cmd_freq = CMD_FREQ|0x620; // 433.92 MHz
#ifdef RFM01
uint16_t cmd_afc = CMD_AFC|AFC_ON|AFC_OUT_ON|AFC_MANUAL|AFC_FINE|AFC_RL_7;
uint16_t cmd_dcycle = CMD_LOWDUTY|0x00;
uint16_t cmd_fifo = CMD_FIFO|0x00;
uint16_t cmd_config = CMD_CONFIG|BAND_433|LOAD_CAP_12C0|BW_67;
uint16_t cmd_rcon = (CMD_RCON|RX_EN|VDI_DRSSI|LNA_0|RSSI_91);
//uint16_t cmd_rcon = (CMD_RCON|RX_EN|VDI_DRSSI|LNA_14|RSSI_97);
uint16_t cmd_dfilter = (CMD_DFILTER|CR_LOCK_FAST|FILTER_OOK);
#endif
#ifdef RFM12B
uint16_t cmd_config = 0x8017;
uint16_t cmd_power = 0x8281; // RFM01 doesn't support this
uint16_t cmd_sync = 0xce55;
uint16_t cmd_afc = 0xc407; // or C400 for no AFC. C6xx on RFM01
uint16_t cmd_dcycle = 0xc800;
uint16_t cmd_pll = 0xcc1f;
uint16_t cmd_fifo = 0xca8a; // CExx rather than CAxx on RFM01
uint16_t cmd_dfilter = 0xc260;
uint16_t cmd_rcon = (CMD_RCON|P16|VDI_MEDIUM|LNA_MEDIUM|RSSI_97|BW_340);
#endif
void strobe_afc(int fd) {
send_command16(fd, cmd_afc|AFC_STROBE); // Strobe high
send_command16(fd, cmd_afc & (~AFC_ON)); // Strobe low, disable AFC processing
uint16_t status = send_command16(fd, cmd_status);
// get offs bits and extend two's complement to a byte
int8_t offset = (status & STATUS_OFFS) | (status & STATUS_OFFSIGN ? 0xe0 : 0);
float freq_offs = (float)offset;
#ifdef RFM12B
freq_offs *= 2.5;
#endif
send_command16(fd, cmd_afc); // Strobe low, re-enable AFC
printf("Frequency deviation %0.1fKHz (%d)\n", freq_offs, (int)offset);
send_command16(fd, cmd_rcon);
}
/*
* Sample the DRSSI flag at 'interval' microsecond intervals over a period of 'duration' ms,
*and return the average.
*/
float sample_rssi(int fd, int duration, int interval) {
unsigned int start_time, now;
unsigned int loop_count = 0, rssi_total = 0;
start_time = TIMER_ARM_COUNT;
do {
uint16_t status = send_command16(fd, cmd_status);
int rssi = (status & STATUS_RSSI) ? 1 : 0;
loop_count++;
rssi_total+=rssi;
now = TIMER_ARM_COUNT;
usleep(interval); // microseconds
} while(now - start_time < (duration * 1000)); // duration as microseconds
float duty = ((float)rssi_total/loop_count) * 100;
return duty;
}
// pressure function and value
extern int read_bmp085(float altitude);
extern float pressure_hpa;
int main(int argc, char *argv[])
{
//unsigned char bytes2[] = {0xa1,0x82,0x0a,0x59,0x03,0x06,0x00,0x4e,0x06,0xc8};
//calculate_values(bytes2);
//return -1;
// initialize weather underground module
WUnderground_Init();
uint8_t packet_sig = 0xfa;
if(map_peripheral(&gpio) == -1 || map_peripheral(&timer_arm) == -1) {
printf("Failed to map the GPIO or TIMER registers into the virtual memory space.\n");
return -1;
}
// 0xF90200; // run at 1MHz
TIMER_ARM_CONTROL = TIMER_ARM_C_DISABLE|TIMER_ARM_C_FREE_EN
|TIMER_ARM_C_16BIT|TIMER_ARM_C_PS1
|TIMER_ARM_C_FPS(0xf9);
// Init GPIO21 (on pin 13) as input (DATA), GPIO22 (pin 15) as output (nRES)
//*(gpio.addr + 2) = (*(gpio.addr + 2) & 0xfffffe07)|(0x001 << 6);
// Init GPIO27
*(gpio.addr + 2) = (*(gpio.addr + 2) & 0xff1fffff);
#ifdef RFM01
printf("Initialising RFM01\n");
#endif
#ifdef RFM12B
printf("Initialising RFM12b\n");
#endif
int fd;
fd = open(device, O_RDWR);
if (fd < 0)
pabort("can't open device");
// SPI mode
if(ioctl(fd, SPI_IOC_WR_MODE, &mode) == -1)
pabort("Can't set SPI mode");
// Bits per word (driver only supports 8 -bits I think, but RFM12B handles this ok)
if(ioctl(fd, SPI_IOC_WR_BITS_PER_WORD, &bits) == -1)
pabort("Can't set bits per word");
// SPI clock speed (Hz)
if(ioctl(fd, SPI_IOC_WR_MAX_SPEED_HZ, &speed) == -1)
pabort("Can't set SPI clock speed");
printf("SPI: mode %d, %d-bit, %d KHz\n", mode, bits, speed/1000);
// LED on
*(gpio.addr + (0x1c >> 2)) = 1 << 22;
// Reset the module? Maybe use software reset if needed.
//send_command(fd, cmd_fifo); // in case reset sensitivity is low
//send_command(fd, cmd_reset);
usleep(100000);
// LED off
*(gpio.addr + (0x28 >> 2)) = 1 << 22;
send_command16(fd, cmd_status);
send_command16(fd, cmd_config);
send_command16(fd, cmd_freq);
send_command16(fd, cmd_drate);
send_command16(fd, cmd_rcon);
send_command16(fd, cmd_dfilter);
send_command16(fd, cmd_fifo);
send_command16(fd, cmd_afc);
send_command16(fd, cmd_dcycle);
#ifdef RFM12B
send_command16(fd, cmd_power);
send_command16(fd, cmd_sync);
send_command16(fd, cmd_pll);
#endif
printf("Ctrl+C to exit\n");
usleep(5000); // Allow crystal oscillator to start
int idx1, idx2;
for(idx1=0; idx1 < 24; idx1++) {
uint16_t cmd_rcon_mod = (cmd_rcon & ~(RSSI_X2|LNA_XX)) | (rssi_scale[idx1].rssi_setth |rssi_scale[idx1].g_lna);
printf("%15s idx %-2d ", rssi_scale[idx1].name, idx1);
for(idx2=0; idx2 < 6; idx2++) {
uint16_t cmd_config_mod = (cmd_config & ~BW_X2) | bw_scale[idx2];
send_command16(fd, cmd_config_mod);
send_command16(fd, cmd_rcon_mod);
usleep(1000);
rssi_scale[idx1].duty[idx2] = sample_rssi(fd, 25, 100);
if(cmd_rcon_mod == cmd_rcon && cmd_config_mod == cmd_config)
printf("%6.2f< ", rssi_scale[idx1].duty[idx2]);
else
printf("%6.2f ", rssi_scale[idx1].duty[idx2]);
fflush(stdout);
}
printf("\n");
}
send_command16(fd, cmd_config);
send_command16(fd, cmd_rcon);
usleep(1000);
// Show the average RSSI to indicate noise at startup. If args dictate
// then repeat forever. Note that an unshielded Ethernet cable will
// radiate noise, so include a delay to allow console output to be flushed.
do {
float duty = sample_rssi(fd, 250, 100);
printf("RSSI Duty %0.2f\r", duty);
fflush(stdout);
usleep(250000);
} while(argc > 1);
printf("\n");
uint16_t status;
uint8_t rssi = 0, oldrssi = 0;
unsigned int shorts = 0;
unsigned int rssitime, oldrssitime, now;
int count = 0, timeout = 1;
time_t last_valid = time(0);
int crc_passed;
unsigned int rssitime_buf[500];
unsigned char bytes[10];
oldrssitime = TIMER_ARM_COUNT;
// Switch to realtime scheduler
scheduler_realtime();
do {
// Read the GPIO pin for clocked DATA value
status = ((*(gpio.addr + 13)) >> 27) & 1;
rssi = status;
rssitime = TIMER_ARM_COUNT;
// Check if the pin transitioned
if(rssi != oldrssi) {
// If falling edge (1 -> 0), then store bit pulse duration
if(rssi == 0) {
rssitime_buf[count] = rssitime - oldrssitime;
if(++count == 500)
count = 499;
}
oldrssi = rssi;
oldrssitime = rssitime;
timeout = 0;
}
// Check time since last transition. If timeout, then dump packet.
int packet_offset = 0;
now = TIMER_ARM_COUNT;
if(!timeout && (now - oldrssitime) > 5000) { // && count > 0
uint8_t sig_matched = 0;
if(count > 60) { // then maybe something at least interesting
// Look for device_id
int idx;
uint8_t bit, sig_in = 0;
for(idx=0; idx < count; idx++) {
bit = rssitime_buf[idx] < g_low_threshold ? 1 : 0;
sig_in = (sig_in << 1) | bit;
if((sig_matched = (sig_in == packet_sig))) {
packet_offset = idx - 3;
break;
}
}
printf("\rData bits = %d (offset %d) (%d short) %s\n",
count, packet_offset, shorts, sig_matched ? "Packet signature found" : "No packet signature found");
if(count == 88 && sig_matched) { // then probably a data packet
// LED on
*(gpio.addr + (0x1c >> 2)) = 1 << 22;
strobe_afc(fd); // lock frequency to good signal
int b;
uint8_t byte;
for(idx=0; idx < 10; idx++) {
byte = 0;
for(b=0; b < 8; b++) {
// Short pulses 1, long pulses 0
uint8_t bit = rssitime_buf[packet_offset + (idx * 8 + b)] < g_low_threshold ? 1 : 0;
byte = (byte << 1) + bit;
}
bytes[idx] = byte;
printf("%02x ", byte);
}
crc_passed = bytes[9] == _crc8(bytes, 9);
printf("crc %s (gap %ds)\n", crc_passed ? "ok" : "fail", (int)(time(0) - last_valid));
last_valid = time(0);
fflush(stdout);
}
} else {
if(shorts++ % 10 == 0) {
printf(".");
fflush(stdout);
}
}
timeout = 1;
// If we get enough bits, then dump stats to indicate pulse lengths coming from the device.
if(count > 40) {
// These are slightly confusing - lo used to mean low side of threshold, but printf below reports them as binary
// 0 and 1. So the meanings are opposite - to be fixed.
unsigned int idx, min_lo=999999, min_hi=999999, max_lo = 0, max_hi = 0;
unsigned int val;
for(idx = 0; idx < count; idx++) {
// printf("RSSI 1 -> 0 %3d: %4dus ( %s )\n", idx, rssitime_buf[idx],
// rssitime_buf[idx] >= LOW_THRESHOLD ? "Hi" : "Lo");
val = rssitime_buf[idx];
// Short pulses are binary '1', long pulses are binary '0'
if(val < g_low_threshold) {
if(val < min_lo)
min_lo = val;
if(val > max_lo)
max_lo = val;
} else {
if(val < min_hi)
min_hi = val;
if(val > max_hi)
max_hi = val;
}
}
printf("Pulse stats: Hi: %u - %u Lo: %u - %u (%d point)\n", min_lo, max_lo, min_hi, max_hi, count);
// Recalculate the pulse threshold if we got a perfect read.
if(count == 88 && crc_passed) {
//g_low_threshold = ( ((max_lo + min_lo) / 2) + ((max_hi + min_hi) / 2)) / 2;
g_low_threshold =(max_lo + min_hi) / 2;
printf("Threshold now %d\n", g_low_threshold);
// Note the time of the last reading...
unsigned int wait_start = TIMER_ARM_COUNT, elapsed;
// at this point, we can do other stuff that requires the RT scheduler
#ifdef USE_BMP085
read_bmp085(ALTITUDE_M); // read pressure, calculate for the given altitude
#endif
calculate_values(bytes, pressure_hpa);
// Wait for remainder of 47 seconds in standard scheduler until we can expect the next read
scheduler_standard();
do {
elapsed = (TIMER_ARM_COUNT - wait_start) / 1000000;
printf("Wait %us \r", 47 - elapsed);
fflush(stdout);
usleep(250000);
} while(elapsed < 47);
printf("Listening for transmission\n");
scheduler_realtime();
}
}
count = 0;
// LED off
*(gpio.addr + (0x28 >> 2)) = 1 << 22;
}
usleep(5); // No point running with nanosecond loops when pulses are in the hundreds of microseconds...
} while(1); // Ctrl+C to exit for now...
// Currenty unreachable
close(fd);
unmap_peripheral(&gpio);
unmap_peripheral(&timer_arm);
return 0;
}
char *direction_name[] = {"N", "NNE", "NE", "ENE", "E", "ESE", "SE", "SSE", "S", "SSW", "SW", "WSW", "W", "WNW", "NW", "NNW"};
void calculate_values(unsigned char *buf, float pressure_hpa) {
unsigned short device_id = ((unsigned short)buf[0] << 4) | (buf[1] >> 4);
unsigned short temperature_raw = (((unsigned short)buf[1] & 0x0f) << 8) | buf[2];
float temperature = ((float)temperature_raw - 400) / 10;
int humidity = buf[3];
unsigned short wind_avg_raw = (unsigned short)buf[4];
float wind_avg_ms = roundf((float)wind_avg_raw * 34.0f) / 100;
float wind_avg_mph = wind_avg_ms * 2.23693629f;
unsigned short wind_gust_raw = (unsigned short)buf[5];
float wind_gust_ms = roundf((float)wind_gust_raw * 34.0f) / 100;
float wind_gust_mph = wind_gust_ms * 2.23693629f;
unsigned short rain_raw = (((unsigned short)buf[6] & 0x0f) << 8) | buf[7];
float rain = (float)rain_raw * 0.3f;
int direction = buf[8] & 0x0f;
char *direction_str = direction_name[direction];
printf("Station Id: %04X\n", device_id);
printf("Temperature: %0.1fC, Humidity: %d%%\n", temperature, humidity);
printf("Wind speed: %0.2f m/s, Gust Speed %0.2f m/s, %s\n", wind_avg_ms, wind_gust_ms, direction_str);
printf("Wind speed: %0.1f mph, Gust Speed %0.1f mph, %s\n", wind_avg_mph, wind_gust_mph, direction_str);
printf("Total rain: %0.1f mm\n", rain);
printf("Pressure (sea level): %0.1f hpa\n", pressure_hpa);
// submit observation to weather underground
WUnderground_Observation(temperature, humidity, wind_avg_mph, wind_gust_mph, direction_str, rain, pressure_hpa);
}
/*
* Function taken from Luc Small (http://lucsmall.com), itself
* derived from the OneWire Arduino library. Modifications to
* the polynomial according to Fine Offset's CRC8 calulations.
*/
uint8_t _crc8( uint8_t *addr, uint8_t len)
{
uint8_t crc = 0;
// Indicated changes are from reference CRC-8 function in OneWire library
while (len--) {
uint8_t inbyte = *addr++;
uint8_t i;
for (i = 8; i; i--) {
uint8_t mix = (crc ^ inbyte) & 0x80; // changed from & 0x01
crc <<= 1; // changed from right shift
if (mix) crc ^= 0x31;// changed from 0x8C;
inbyte <<= 1; // changed from right shift
}
}
return crc;
}
void scheduler_realtime() {
struct sched_param p;
p.__sched_priority = sched_get_priority_max(SCHED_RR);
if( sched_setscheduler( 0, SCHED_RR, &p ) == -1 ) {
perror("Failed to switch to realtime scheduler.");
}
}
void scheduler_standard() {
struct sched_param p;
p.__sched_priority = 0;
if( sched_setscheduler( 0, SCHED_OTHER, &p ) == -1 ) {
perror("Failed to switch to normal scheduler.");
}
}
Andy