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Introduces version-specific config & condition BLE lux encoding

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In the BLE service data payload, one of the reserved bits is now used to
indicate whether or not the ambient lux value is encoded in the packet.
Bit 0 of the first byte is now the `has_lux` bit. If it is set, bytes
16-17 in the service data will contain the ambient lux. If `has_lux` is
not set, bytes 16-17 may not exist (for compatibility with older
firmwares) or may hold meaningless values.

This commit also introduces version-specific configuration in
prst_config.h. Photoresistor config, for example, is only meaninful for
version 1.1.x.
This commit is contained in:
rbaron 2021-09-22 22:23:08 +02:00
parent a00559a98b
commit d8aea1d4ef
4 changed files with 83 additions and 31 deletions
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30
code/b-parasite/README.md
View file

@ -30,16 +30,26 @@ Sensor data is encoded in the BLE advertisement packet as Service Data for the [
Sensor data is encoded in unsigned 16 bits (2 bytes), and whenever multiple
bytes are used to represent a single value, the encoding is big-endian.
| Byte index | Description |
|------------|----------------------------------------------------------------|
| 0 | 4 bits for protocol version + 4 reserved bits |
| 1 | 4 reserved bits + 4 bits wrap-around counter for deduplication |
| 2-3 | Battery voltage in millivolts |
| 4-5 | Temperature in millidegrees Celcius |
| 6-7 | Relative air humidity, scaled from 0 (0%) to 0xffff (100%) |
| 8-9 | Soil moisture, scaled from from 0 (0%) to 0xffff (100%) |
| 10-15 | b-parasite's own MAC address, big-endian format |
| 16-17 | Ambient brightness level from 0 (dark) to 0xffff (bright) |
| Byte index | Description |
|------------|-----------------------------------------------------------------|
| 0 | Protocol version (4 bits) + reserved (3 bits) + has_lux* (1 bit)|
| 1 | Reserved (4 bits) + increasing, wrap-around counter (4 bits) |
| 2-3 | Battery voltage in millivolts |
| 4-5 | Temperature in millidegrees Celcius |
| 6-7 | Relative air humidity, scaled from 0 (0%) to 0xffff (100%) |
| 8-9 | Soil moisture, scaled from from 0 (0%) to 0xffff (100%) |
| 10-15 | b-parasite's own MAC address |
| 16-17* | Ambient light in lux |
\* If the `has_lux` bit is set, bytes 16-17 shall contain the ambient light in lux.
If the `has_lux` bit is not set, bytes 16-17 may not exist or may contain
meaningless data. The reasons for this behavior are:
1. b-parasite version 1.0.x has no light sensor and its advertisement data may
have only 16 bytes if its using an older firmware. In this case, `has_lux` shall
never be set;
2. b-parasite version 1.1.x has space for an optional LDR. Users can configure
whether or not they have added the LDR by setting the `PRST_HAS_LDR` to 1 in
prst_config.h.
# Supported Modules

27
code/b-parasite/config/prst_config.h
View file

@ -3,13 +3,15 @@
#include "nrf_gpio.h"
// Some configurations are version-specific. Uncomment the line corresponding
// the the version you're programming. The version can be found on the
// b-parasite board.
// #define PRST_VERSION_1_0_X
#define PRST_VERSION_1_1_X
// Built-in LED.
#define PRST_LED_PIN NRF_GPIO_PIN_MAP(0, 28)
// Photoresistor pins.
#define PRST_PHOTO_V NRF_GPIO_PIN_MAP(0, 29)
#define PRST_PHOTO_OUT NRF_GPIO_PIN_MAP(0, 2)
// Deep sleep.
#define PRST_DEEP_SLEEP_IN_SECONDS 2
@ -18,7 +20,6 @@
// moisture.
#define PRST_ADC_BATT_DEBUG 0
#define PRST_ADC_SOIL_DEBUG 0
#define PRST_ADC_PHOTO_DEBUG 1
// BLE.
// Prints out BLE debug info, such as the final encoded advertisement packet.
@ -50,4 +51,20 @@
// SHT3C temp/humidity sensor.
#define PRST_SHT3C_DEBUG 0
// Version-specific configuration.
#if defined(PRST_VERSION_1_1_X)
// The photoresistor (LDR) is optional in this revision. If set to 1, the LDR's
// ADC channel will be sampled and its data will be encoded in the BLE
// advertisement packet.
#define PRST_HAS_LDR 1
// Light sensor pins.
#define PRST_PHOTO_V_PIN NRF_GPIO_PIN_MAP(0, 29)
#define PRST_PHOTO_OUT_PIN NRF_GPIO_PIN_MAP(0, 2)
// Whether to produce debug messages for the LDR
#define PRST_ADC_PHOTO_DEBUG 1
#endif // End of version-specific configuration.
#endif // _PRST_CONFIG_H_

16
code/b-parasite/src/main.c
View file

@ -26,7 +26,9 @@ static void log_init(void) {
static void gpio_init(void) {
nrf_gpio_cfg_output(PRST_LED_PIN);
nrf_gpio_cfg_output(PRST_FAST_DISCH_PIN);
nrf_gpio_cfg_output(PRST_PHOTO_V);
#ifdef PRST_HAS_LDR
nrf_gpio_cfg_output(PRST_PHOTO_V_PIN);
#endif
NRF_LOG_INFO("GPIO pins inited.");
}
@ -64,13 +66,17 @@ static void rtc_callback() {
prst_pwm_stop();
nrf_gpio_pin_clear(PRST_FAST_DISCH_PIN);
nrf_gpio_pin_set(PRST_PHOTO_V);
uint16_t lux = 0;
#ifdef PRST_HAS_LDR
nrf_gpio_pin_set(PRST_PHOTO_V_PIN);
prst_adc_photo_sensor_t photo_read = prst_adc_photo_read(batt_read.voltage);
nrf_gpio_pin_clear(PRST_PHOTO_V);
nrf_gpio_pin_clear(PRST_PHOTO_V_PIN);
lux = photo_read.brightness;
#endif
prst_ble_update_adv_data(batt_read.millivolts, temp_humi.temp_millicelcius,
temp_humi.humidity, soil_read.relative,
photo_read.brightness, run_counter);
temp_humi.humidity, soil_read.relative, lux,
run_counter);
prst_adv_start();
nrf_delay_ms(PRST_BLE_ADV_TIME_IN_MS);
prst_adv_stop();

41
code/b-parasite/src/prst/ble.c
View file

@ -24,17 +24,28 @@
// Sensor data is encoded in unsigned 16 bits (2 bytes), and whenever multiple
// bytes are used to represent a single value, the encoding is big-endian:
/*
| Byte index | Description |
|------------|----------------------------------------------------------------|
| 0 | 4 bits for protocol version + 4 reserved bits |
| 1 | 4 reserved bits + 4 bits wrap-around counter for deduplication |
| 2-3 | Battery voltage in millivolts |
| 4-5 | Temperature in millidegrees Celcius |
| 6-7 | Relative air humidity, scaled from 0 (0%) to 0xffff (100%) |
| 8-9 | Soil moisture, scaled from from 0 (0%) to 0xffff (100%) |
| 10-15 | b-parasite's own MAC address |
| 16-17 | Ambient brightness level from 0 (dark) to 0xffff (bright) |
| Byte index | Description |
|------------|-----------------------------------------------------------------|
| 0 | Protocol version (4 bits) + reserved (3 bits) + has_lux* (1 bit)|
| 1 | Reserved (4 bits) + increasing, wrap-around counter (4 bits) |
| 2-3 | Battery voltage in millivolts |
| 4-5 | Temperature in millidegrees Celcius |
| 6-7 | Relative air humidity, scaled from 0 (0%) to 0xffff (100%) |
| 8-9 | Soil moisture, scaled from from 0 (0%) to 0xffff (100%) |
| 10-15 | b-parasite's own MAC address |
| 16-17* | Ambient light in lux |
* If the has_lux bit is set, bytes 16-17 shall contain the ambient light in lux.
If the has_lux bit is not set, bytes 16-17 may not exist or may contain
meaningless data. The reasons for this behavior are:
1. b-parasite version 1.0.0 has no light sensor and its advertisement data may
have only 16 bytes if its using an older firmware. In this case, has_lux shall
never be set;
2. b-parasite version 1.1.0 has space for an optional LDR. Users can configure
whether or not they have added the LDR by setting the PRST_HAS_LDR to 1 in
prst_config.h.
*/
#define SERVICE_DATA_LEN 18
static uint8_t service_data[SERVICE_DATA_LEN];
@ -99,7 +110,13 @@ static void init_advertisement_data() {
APP_ERROR_CHECK(err_code);
// Four bits for the protocol version.
service_data[0] = (PRST_BLE_PROTOCOL_VERSION << 4) & 0xf0;
service_data[0] |= (PRST_BLE_PROTOCOL_VERSION << 4) & 0xf0;
// Bit 0 of byte 0 specifies whether or not ambient light data exists in the
// payload.
#if PRST_HAS_LDR
service_data[0] |= 1;
#endif
// Parses configured MAC address from PRST_BLE_MAC_ADDR.
int mac_bytes[6];
@ -154,8 +171,10 @@ void prst_ble_update_adv_data(uint16_t batt_millivolts,
service_data[8] = soil_moisture >> 8;
service_data[9] = soil_moisture & 0xff;
#ifdef PRST_HAS_LDR
service_data[16] = brightness >> 8;
service_data[17] = brightness & 0xff;
#endif
// Encodes adv_data_ into .gap_adv_data_.
uint32_t err_code = ble_advdata_encode(