Ble Plant sensor chip TLSR8250

[finipini]

Hi i have a ble Plant sensor ( a bit like Xiaomi mi flora ) that have the chip TLSR8250, i wonder if this could be compatible with zigbee and what i could do to test it.

[pvvx]

TLSR8250 can work in Zigbee. But this sensor uses an additional circuit, which is not very optimal for measuring soil moisture and has a high battery consumption. I try to avoid sensors with sub-optimal battery consumption due to further numerous user complaints.

[finipini]

TLSR8250 can work in Zigbee. But this sensor uses an additional circuit, which is not very optimal for measuring soil moisture and has a high battery consumption.

Oh ok. One good thing about the sensor os that uses 2 AAA batteries that is easy to have rechargable ones. Never really use it in plants yet, but if it is not reliable maybe should forget this.

[pvvx]

The most commonly used scheme is similar to:

https://tlfong01.blog/2020/09/26/moisture-sensor-notes-2/

[pvvx]

For operation, the required frequency must be in the region of several MHz. The signal should not be rectangular, it should have different half-cycles to bias the diode. No external 555 timer is required. TLSR825x has more advanced built-in PWM controllers. An acceptable TLSR825x circuit contains one resistor, one capacitor and one RF diode. The measurement time ranges from 5 to 16 ms, depending on the size (capacity) of the sensor itself. The total current consumption of the entire device when measured does not exceed 3 mA. No one will remake the purchased sensors. And I am not in the commercial or household goods business.

[pvvx]

From my archive:

The duty cycle of the PWM is tuned for the DC component of the voltage drop across the diode.

For real example (Soc:TLSR8253), set the PWM parameters to 1/12. Those. cycle = 12 periods 24 MHz, of which 1 period is an impulse. Total frequency over the period - 2 MHz. Pulse envelope - 12 MHz. R=7.5к, C=100nF.

The final sensitivity on the probe is less than 1 pF. A piece of wires in a couple of cm is a sensor for bringing the hand to the case (checking for XiaomiLYWSD03MMC through its case). The voltage with the hand drops to 350 mV and below. Without - more than 405 mV. Test without setting the duty cycle and duration of PWM. Automatic adjustment of PWM parameters for any sensors is possible and uncomplicated.

At C=10 nF, the measurement time is up to 2 ms.

Measurement in this case takes up to 2 ms with current consumption up to (!) 5 mA. If measurements are made every minute, then the consumption per measurement will be: (0.002sec*0.005A)/60sec = 0.000000167A = 0.167uA It is necessary to add to it the sleep current (power on: SRAM and RTC) of the SoC - 1.8 uA. When advertising is broadcast every 3 seconds, the average SoC consumption is 5..7 uA. Depends on the transmission encoding. The data is given and consistent with the real test on SoC TLSR8253.

/*
 * rh.c
 *
 *  Created on: 05.04.2022
 *      Author: pvvx
 */
#include <stdint.h>
#include "tl_common.h"
#include "drivers.h"
#include "battery.h"

// R = 7.5 kOm, BAV99, C 10..100 nF

/*********************************************************************************
    PWM0   :  PA2.  PC1.  PC2.  PD5
    PWM1   :  PA3.  PC3.
    PWM2   :  PA4.  PC4.
    PWM3   :  PB0.  PD2.
    PWM4   :  PB1.  PB4.
    PWM5   :  PB2.  PB5.
    PWM0_N :  PA0.  PB3.  PC4   PD5
    PWM1_N :  PC1.  PD3.
    PWM2_N :  PD4.
    PWM3_N :  PC5.
    PWM4_N :  PC0.  PC6.
    PWM5_N :  PC7.
 *********************************************************************************/

#define PWM_PIN     GPIO_PB5
#define AS_PWMx     AS_PWM5
#define PWM_ID      PWM5_ID

static void pwm_init(void) {
    reg_clk_en0 |= FLD_CLK0_PWM_EN;
    reg_pwm_clk = 0; // = CLOCK_SYS_CLOCK_HZ 24Mhz
    pwm_set_mode(PWM_ID, PWM_NORMAL_MODE);
    pwm_set_phase(PWM_ID, 0);   //no phase at pwm beginning
    pwm_set_cycle_and_duty(PWM_ID, 12, 1);
    pwm_start(PWM_ID);
    gpio_set_func(PWM_PIN, AS_PWMx);
}

extern void adc_channel_init(ADC_InputPchTypeDef p_ain);

uint16_t get_adc_rh_mv(uint32_t p_ain) { // ADC_InputPchTypeDef
    gpio_setup_up_down_resistor(GPIO_ADC1, PM_PIN_UP_DOWN_FLOAT);
    pwm_init();
#if 0
    u32 t0 = clock_time();
    while (!clock_time_exceed(t0, 10000));
#else
    pm_wait_us(16000);
#endif
#if 1
    uint16_t mv = get_adc_mv(p_ain);
    pwm_stop(PWM_ID);
    gpio_setup_up_down_resistor(GPIO_ADC1, PM_PIN_PULLDOWN_100K);
    return mv;
#else
#define ADC_BUF_COUNT   8
    volatile unsigned int adc_dat_buf[ADC_BUF_COUNT];
    adc_channel_init(VBAT);
    adc_power_on_sar_adc(1); // + 0.4 mA
    adc_reset_adc_module();
    adc_set_ain_chn_misc(p_ain, GND);
    pm_wait_us(200);
    adc_config_misc_channel_buf((uint16_t *) adc_dat_buf, sizeof(adc_dat_buf));
    adc_dat_buf[ADC_BUF_COUNT-1]=0;
    dfifo_enable_dfifo2();
    pm_wait_us(100);
    pwm_stop(PWM_ID);
    while(adc_dat_buf[ADC_BUF_COUNT-1]==0);
    dfifo_disable_dfifo2();
    gpio_setup_up_down_resistor(GPIO_PB7, PM_PIN_PULLDOWN_100K);
    adc_power_on_sar_adc(0); // - 0.4 mA
    u32 adc_average = 0;
    int i;
    for (i = 0; i < ADC_BUF_COUNT; i++)
            adc_average += ((uint16_t) adc_dat_buf[i] & 0x3FFF);
    return (adc_average * adc_vref_cfg.adc_vref) >> (10 + 3);
#endif
}

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Similarly, it is possible to build a completely isolated water leak sensor.