Wirnet™ iBTS: Power supply management

The Wirnet iBTS gateway can be powered with an Ethernet cable (PoE injector) or/and an auxiliary power supply (solar panel, battery). When both PoE and external power supply are plugged, the gateway uses the highest voltage available.

Power loss can be detected by polling the value of the VIN_9V signal. It should fall down near 0V when both, PoE and Aux power, are lost. The first action to take when the VIN_9V value decreases is to stop the LoRa module. This will decrease the consumption so the gateway will have enough time to stop. The voltage value can be obtained with the following methods:

Get the value VIN_POE with the tool sensors:

root@klk-lpbs-0605F5:~# sensors | grep POE                                                                                                                                                             
VIN_POE:     +52.61 V

or, in C with lmsensors library:

#include <sensors/sensors.h>
 
static int get_sensor_voltage(const char * pName, double * pVoltage)
{
  const sensors_chip_name *chip;
  const sensors_feature *feature;
  const sensors_subfeature * subfeature;
  int chip_nr, i;
  char *label = NULL;
  double voltage = 0;
  int result = -1;
  int ret;
 
  ret = sensors_init(NULL);
  if (ret != 0) {
    syslog(LOG_ERR, "[%s:%d] err %d in sensors_init\n", __FUNCTION__, __LINE__, ret);
    return result;
  }
 
  chip_nr = 0;
  while ((chip = sensors_get_detected_chips(NULL, &chip_nr))) {
    i = 0;
    while ((feature = sensors_get_features(chip, &i))) {
      label = sensors_get_label(chip, feature);
      if (label != NULL) {
        subfeature = sensors_get_subfeature(chip, feature, SENSORS_SUBFEATURE_IN_INPUT);
        if ((strcmp(pName, label) == 0) && (subfeature != NULL)) {
          if (sensors_get_value(chip, subfeature->number, &voltage) == 0) {
            *pVoltage = voltage;
            result = 0;
          }
        }
        free(label);
        label = NULL;
      }
    }
  }
  sensors_cleanup();
  return result;
}
 
double voltage = 0;
 
get_sensor_voltage("VIN_POE", &voltage);

On older releases (click to expand)

root@klk-lpbs:~# adc 4
VIN_9V=48979mV

  FILE * pf_file = NULL;
  u32    u32_adc_value = 0;
 
  pf_file = fopen ("/sys/bus/iio/devices/iio:device1/in_voltage0_raw", "r");
  if(pf_file != NULL)
  {
    fscanf (pf_file, "%d\n", &value);
    fclose (pf_file);
    pf_file = NULL;
  }
  u32_adc_value=( (value * 3300) / 4096 );
  u32_adc_value = ((u32_adc_value* 485) / 15);

Since version 4.2, All internal voltage measurement can be obtained using the following tool:

root@klk-lpbs-0605F5:~# sensors 
klk_lpbs_adc-isa-0000
Adapter: ISA adapter
VDD_CORE:     +1.37 V  
NVCC_DRAM:    +1.35 V  
3V3_FDP:      +3.30 V  
NVCC_3V3:     +3.30 V  
VIN_POE:     +52.61 V  
VCC_5V:       +5.03 V  
VPOWER:       +9.05 V  
VPORT_MEAS:  +53.19 V  

On all versions, you can also use the following tool:

root@klk-lpbs:~# adc
VDD_CORE=1372mV
NVCC_DRAM=1354mV
3V3_FDP=3283mV
NVCC_3V3=3288mV
VIN_9V=48435mV
VCC_5V=5008mV
VPOWER=9139mV
VPORT_MEAS=48435mV