WMPRO FW >= 1.0 WMMEGA FW >= 2.0

Read an onboard ADC channel

Return the raw ADC value of a channel

$channel: Value between 0 and 2

Channel 0 is attached to pin A1, which is the voltage divider to measure battery voltage and can measure up to 60V DC.

Channel 1 is connected to pin A2 which can handle up to 330V DC.

Channel 2 is connected to pin A3, which reads 0-5V DC.

Integer ADC value:

WMPRO 10-bit, 0-1023

WMMEGA 12-bit, 0-4095

Read Channel 0 and use the constants v_adc_offset and v_adc_mul to obtain a calibrated voltage¹⁾:

<pre><? 
  $adc=adc_read(0);
  $volts=floatval($_GLOBALS['v_adc_mul'])*(floatval($adc)+floatval($_GLOBALS['v_adc_offset']));
  print("adc=".$adc."\r\n");
  print("v_adc_offset=".$_GLOBALS['v_adc_offset']."\r\n");
  print("v_adc_mul=".$_GLOBALS['v_adc_mul']."\r\n");
  print("volts=".$volts."\r\n");
?></pre>

Typical output for the above example (results vary depending on actual voltage and calibration constants):

adc=192
v_adc_offset=24.811435
v_adc_mul=0.065411
volts=14.181854

The raw ADC values can be accessed using adc_read(), but it is recommended to use the functions mb_get_val_by_role() or mb_get_dev_by_id() in order to obtain calculated values for A1, A2 and A3 that are adjusted by the calibration values stored in NVRAM.

Use mb_get_dev_by_id() to obtain calibrated values for A1, A2 and A3:

<pre><?
  $dev=mb_get_dev_by_id(0);
  $a1=$dev['a1']/10;  // scaled by 10
  $a2=$dev['a2']/10;  // scaled by 10
  $a3=$dev['a3']/100; // scaled by 100
  print("A1=".$a1." V\r\n");
  print("A2=".$a2." V\r\n");
  print("A3=".$a3." V\r\n");
?></pre>

Typical output for the above example (results vary depending on actual voltage and calibration constants):

A1=13.600001 V
A2=2.100000 V
A3=4.980000 V

uphp_special_variables - Special arrays that are populated automatically (including $_GLOBALS)

pin_configure() - Configure an I/O pin as a digital input, output, or analog input [for more information on Channel numbers which are also known as Pin Indexes]

floatval() - Return the float value of a number or string