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adc_read
WMPRO FW >= 1.0 WMMEGA FW >= 2.0
Read an onboard ADC channel
Description
Parameter
$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.
Return Value
WMPRO ADC value (10-bit), 0-1023
WMMEGA ADC value (12-bit), 0-4095
Examples
Example #1 - 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
Additional Information
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.
Example #2 - 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
See Also
uphp_special_variables - Special arrays that are populated automatically (including $_GLOBALS)
floatval() - Return the floating point value of a number or string
