ADC attenuation for ESP32 targets (ExpressLRS#2252)

pkendall64 · CapnBry · web-flow · commit cd1fbe8bc013 · 2023-06-21T09:11:04.000+12:00
* Hardware configurable ADC attenuation

* Add -1 option to be able to unset the attenuation value

* Only set ADC attenuation if set

* Add ADC cal characterization option

* Hardware configurable ADC attenuation

* Add -1 option to be able to unset the attenuation value

* Only set ADC attenuation if set

* Add ADC cal characterization option

* Adjustments to VBAT using eFuse calibration

* Final scale/offset for production ERx-xx RXes

---------

Co-authored-by: Bryan Mayland &lt;bmayland@capnbry.net&gt;
diff --git a/src/hardware/RX/Frank 2400.json b/src/hardware/RX/Frank 2400.json
@@ -32,5 +32,6 @@
     "vbat": 34,
     "vbat_offset": 12,
     "vbat_scale": 410,
+    "vbat_atten": 0,
     "button": 0
 }
diff --git a/src/hardware/RX/Generic 2400 True Diversity PA PWM 14.json b/src/hardware/RX/Generic 2400 True Diversity PA PWM 14.json
@@ -32,5 +32,6 @@
 
     "vbat": 36,
     "vbat_offset": -197,
-    "vbat_scale": 1200
+    "vbat_scale": 1200,
+    "vbat_atten": 0
 }
diff --git a/src/hardware/RX/Generic 2400 True Diversity PWM 16.json b/src/hardware/RX/Generic 2400 True Diversity PWM 16.json
@@ -3,15 +3,15 @@
     "radio_mosi":32,
     "radio_rst":25,
     "radio_sck":33,
-    
+
     "radio_busy":37,
     "radio_dio1":38,
     "radio_nss":26,
-    
+
     "radio_busy_2":39,
     "radio_dio1_2":34,
     "radio_nss_2":27,
-    
+
     "power_min":0,
     "power_high":0,
     "power_max":0,
@@ -23,10 +23,11 @@
     "led_rgb_isgrb":true,
     "ledidx_rgb_status":[0],
     "ledidx_rgb_boot":[0],
-    
+
     "pwm_outputs":[14,12,13,15,2,0,4,9,10,5,18,23,19,22,3,1],
 
     "vbat": 36,
     "vbat_offset": -197,
-    "vbat_scale": 1200
+    "vbat_scale": 1200,
+    "vbat_atten": 0
 }
diff --git a/src/hardware/RX/Generic 900 True Diversity PWM 16.json b/src/hardware/RX/Generic 900 True Diversity PWM 16.json
@@ -3,11 +3,11 @@
     "radio_mosi":32,
     "radio_rst":25,
     "radio_sck":33,
-    
+
     "radio_dio0":37,
     "radio_dio1":38,
     "radio_nss":26,
-    
+
     "radio_dio0_2":39,
     "radio_dio1_2":34,
     "radio_nss_2":27,
@@ -23,10 +23,11 @@
     "led_rgb_isgrb":true,
     "ledidx_rgb_status":[0],
     "ledidx_rgb_boot":[0],
-    
+
     "pwm_outputs":[14,12,13,15,2,0,4,9,10,5,18,23,19,22,3,1],
 
     "vbat": 36,
     "vbat_offset": -197,
-    "vbat_scale": 1200
+    "vbat_scale": 1200,
+    "vbat_atten": 0
 }
diff --git a/src/hardware/RX/Radiomaster 2400 ER8G.json b/src/hardware/RX/Radiomaster 2400 ER8G.json
@@ -29,6 +29,7 @@
     "i2c_scl": 18,
     "vbat": 39,
     "button": 0,
-    "vbat_scale": 1280,
-    "vbat_offset": -250
+    "vbat_scale": 700,
+    "vbat_offset": -30,
+    "vbat_atten": 7
 }
diff --git a/src/hardware/RX/Vario 2400.json b/src/hardware/RX/Vario 2400.json
@@ -21,6 +21,7 @@
     "pwm_outputs": [14,1,3,15,2,4],
     "vbat": 39,
     "button": 0,
-    "vbat_scale": 1038,
-    "vbat_offset": -153
+    "vbat_scale": 1024,
+    "vbat_offset": -62,
+    "vbat_atten": 7
 }
diff --git a/src/hardware/targets.json b/src/hardware/targets.json
@@ -106,8 +106,9 @@
                 "layout_file": "Generic 900 True Diversity PWM 16.json",
                 "overlay": {
                     "pwm_outputs":[13,15,2,0,4,9,10,5,18,23,19,22,3,1],
-                    "vbat_offset": -300,
-                    "vbat_scale": 1227
+                    "vbat_offset": 4,
+                    "vbat_scale": 285,
+                    "vbat_atten": 4
                 },
                 "upload_methods": ["uart", "wifi", "betaflight"],
                 "platform": "esp32",
@@ -211,8 +212,9 @@
                 "layout_file": "Generic 2400 True Diversity PA PWM 14.json",
                 "overlay": {
                     "radio_dcdc": true,
-                    "vbat_offset": -300,
-                    "vbat_scale": 1227
+                    "vbat_offset": 4,
+                    "vbat_scale": 285,
+                    "vbat_atten": 4
                 },
                 "upload_methods": ["uart", "wifi", "betaflight"],
                 "platform": "esp32",
diff --git a/src/html/hardware.html b/src/html/hardware.html
@@ -262,6 +262,19 @@ <h1><b>ExpressLRS</b></h1>
 					<tr><td></td><td>VBat pin<img class="icon-analog"/></td><td><input size='3' id='vbat' name='vbat' type='text'/></td><td>Analog input pin for reading VBAT voltage (1V max on 8285, 3.3V max on ESP32)</td></tr>
 					<tr><td></td><td>VBat offset</td><td><input size='7' id='vbat_offset' name='vbat_offset' type='text'/></td><td>Offset and scale are used together with the analog pin to calculate the voltage</td></tr>
 					<tr><td></td><td>VBat scale</td><td><input size='7' id='vbat_scale' name='vbat_scale' type='text'/></td><td>voltage = (analog - offset) / scale</td></tr>
+					<tr><td></td><td>VBat attenuation</td><td>
+						<select id='vbat_atten' name='vbat_atten'>
+							<option value='-1'>Default</option>
+							<option value='0'>0 dB</option>
+							<option value='1'>2.5 dB</option>
+							<option value='2'>6 dB</option>
+							<option value='3'>11 dB</option>
+							<option value='4'>0 dB + calibration</option>
+							<option value='5'>2.5 dB + calibration</option>
+							<option value='6'>6 dB + calibration</option>
+							<option value='7'>11 dB + calibration</option>
+						</select>
+					</td><td>ADC pin attenuation (ESP32) and optional efuse-based calibration adjustment</td></tr>
 
 					<tr><td colspan='2'><b>SPI VTX</td></tr>
 					<tr><td></td><td>RF amp PWM pin<img class="icon-pwm"/></td><td><input size='3' id='vtx_amp_pwm' name='vtx_amp_pwm' type='text'/></td><td>Set the power output level of the VTX PA (value is calculated based on power and frequency using VPD interpolation values)</td></tr>
diff --git a/src/include/hardware.h b/src/include/hardware.h
@@ -123,6 +123,7 @@ typedef enum {
     HARDWARE_vbat,
     HARDWARE_vbat_offset,
     HARDWARE_vbat_scale,
+    HARDWARE_vbat_atten,
 
     // VTX
     HARDWARE_vtx_amp_pwm,
diff --git a/src/lib/AnalogVbat/devAnalogVbat.cpp b/src/lib/AnalogVbat/devAnalogVbat.cpp
@@ -5,15 +5,25 @@
 #include "CRSF.h"
 #include "telemetry.h"
 #include "median.h"
+#include "logging.h"
 
 // Sample 5x samples over 500ms (unless SlowUpdate)
 #define VBAT_SMOOTH_CNT         5
+#if defined(DEBUG_VBAT_ADC)
+#define VBAT_SAMPLE_INTERVAL    20U // faster updates in debug mode
+#else
 #define VBAT_SAMPLE_INTERVAL    100U
+#endif
 
 typedef uint16_t vbatAnalogStorage_t;
 static MedianAvgFilter<vbatAnalogStorage_t, VBAT_SMOOTH_CNT>vbatSmooth;
 static uint8_t vbatUpdateScale;
 
+#if defined(PLATFORM_ESP32)
+#include "esp_adc_cal.h"
+static esp_adc_cal_characteristics_t *vbatAdcUnitCharacterics;
+#endif
+
 /* Shameful externs */
 extern Telemetry telemetry;
 
@@ -33,25 +43,47 @@ static int start()
     }
     vbatUpdateScale = 1;
 #if defined(PLATFORM_ESP32)
-    analogSetPinAttenuation(GPIO_ANALOG_VBAT, ADC_0db);
     analogSetWidth(12);
+
+    int atten = hardware_int(HARDWARE_vbat_atten);
+    if (atten != -1)
+    {
+        // if the configured value is higher than the max item (11dB, it indicates to use cal_characterize)
+        bool useCal = atten > ADC_11db;
+        if (useCal)
+        {
+            atten -= (ADC_11db + 1);
+
+            vbatAdcUnitCharacterics = new esp_adc_cal_characteristics_t();
+            int8_t channel = digitalPinToAnalogChannel(GPIO_ANALOG_VBAT);
+            adc_unit_t unit = (channel > (SOC_ADC_MAX_CHANNEL_NUM - 1)) ? ADC_UNIT_2 : ADC_UNIT_1;
+            esp_adc_cal_characterize(unit, (adc_atten_t)atten, ADC_WIDTH_BIT_12, 3300, vbatAdcUnitCharacterics);
+        }
+        analogSetPinAttenuation(GPIO_ANALOG_VBAT, (adc_attenuation_t)atten);
+    }
 #endif
+
     return VBAT_SAMPLE_INTERVAL;
 }
 
 static void reportVbat()
 {
-    uint32_t adc = vbatSmooth.calc_scaled();
-    uint16_t vbat;
-    // For negative offsets, anything between abs(OFFSET)*CNT and 0 is considered 0
-    if (ANALOG_VBAT_OFFSET < 0 && adc <= (ANALOG_VBAT_OFFSET * -vbatSmooth.scale()))
+    uint32_t adc = vbatSmooth.calc();
+#if defined(PLATFORM_ESP32) && !defined(DEBUG_VBAT_ADC)
+    if (vbatAdcUnitCharacterics)
+        adc = esp_adc_cal_raw_to_voltage(adc, vbatAdcUnitCharacterics);
+#endif
+
+    int32_t vbat;
+    // For negative offsets, anything between abs(OFFSET) and 0 is considered 0
+    if (ANALOG_VBAT_OFFSET < 0 && adc <= -ANALOG_VBAT_OFFSET)
         vbat = 0;
     else
-        vbat = adc * 100U / (ANALOG_VBAT_SCALE * vbatSmooth.scale());
+        vbat = ((int32_t)adc - ANALOG_VBAT_OFFSET) * 100 / ANALOG_VBAT_SCALE;
 
     CRSF_MK_FRAME_T(crsf_sensor_battery_t) crsfbatt = { 0 };
     // Values are MSB first (BigEndian)
-    crsfbatt.p.voltage = htobe16(vbat);
+    crsfbatt.p.voltage = htobe16((uint16_t)vbat);
     // No sensors for current, capacity, or remaining available
 
     CRSF::SetHeaderAndCrc((uint8_t *)&crsfbatt, CRSF_FRAMETYPE_BATTERY_SENSOR, CRSF_FRAME_SIZE(sizeof(crsf_sensor_battery_t)), CRSF_ADDRESS_CRSF_TRANSMITTER);
@@ -64,8 +96,15 @@ static int timeout()
     {
         return DURATION_NEVER;
     }
-    int adc = analogRead(GPIO_ANALOG_VBAT);
-    adc = (adc > ANALOG_VBAT_OFFSET) ? adc - ANALOG_VBAT_OFFSET : 0;
+
+    uint32_t adc = analogRead(GPIO_ANALOG_VBAT);
+#if defined(PLATFORM_ESP32) && defined(DEBUG_VBAT_ADC)
+    // When doing DEBUG_VBAT_ADC, every value is adjusted (for logging)
+    // in normal mode only the final value is adjusted to save CPU cycles
+    if (vbatAdcUnitCharacterics)
+        adc = esp_adc_cal_raw_to_voltage(adc, vbatAdcUnitCharacterics);
+    DBGLN("$ADC,%u", adc);
+#endif
 
     unsigned int idx = vbatSmooth.add(adc);
     if (idx == 0 && connectionState == connected)
diff --git a/src/lib/OPTIONS/hardware.cpp b/src/lib/OPTIONS/hardware.cpp
@@ -117,6 +117,7 @@ static const struct {
     {HARDWARE_vbat, "vbat", INT},
     {HARDWARE_vbat_offset, "vbat_offset", INT},
     {HARDWARE_vbat_scale, "vbat_scale", INT},
+    {HARDWARE_vbat_atten, "vbat_atten", INT},
     {HARDWARE_vtx_amp_pwm, "vtx_amp_pwm", INT},
     {HARDWARE_vtx_amp_vpd, "vtx_amp_vpd", INT},
     {HARDWARE_vtx_amp_vref, "vtx_amp_vref", INT},
diff --git a/src/python/test_tools/power_sweep.py b/src/python/test_tools/power_sweep.py
@@ -0,0 +1,105 @@
+# This script runs an automated voltage sweep while collecting ADC DBGLN() output
+# from an ExpressLRS RX using devAnalogVbat. The receiver should be compiled with:
+#   -DDEBUG_VBAT_ADC -DDEBUG_LOG -DDEBUG_CRSF_NO_OUTPUT -DRCVR_UART_BAUD=460800
+# (lots of UART errors at the default 420000)
+# If firmware is workign correctly `cat /dev/ttyUSB0` will show values such as
+#   $ADC,925
+#   $ADC,924
+#   $ADC,926
+#   ...
+
+# Uses the KoradSerial library for power supply control, just dump this in the library directory
+# https://github.com/starforgelabs/py-korad-serial
+from koradserial import KoradSerial
+import time
+import serial
+import argparse
+
+class MedianAvg:
+    def __init__(self):
+        self.reset()
+    def reset(self):
+        self.vals = []
+        self.min = 0
+        self.max = 0
+        self.mean = 0
+    def add(self, val):
+        self.vals.append(val)
+    def calc(self):
+        if len(self.vals) < 3:
+            self.reset()
+            return
+        self.vals.sort()
+        self.min = self.vals[0]
+        self.max = self.vals[-1]
+        self.mean = 0
+        for i in range(1, len(self.vals)-1):
+            self.mean += self.vals[i]
+        self.mean = self.mean / (len(self.vals)-2)
+    def __len__(self):
+        return len(self.vals)
+    def __str__(self):
+        return f'n={len(self.vals)} mean={self.mean} min={self.min} max={self.max}'
+
+def flushSerial(ser):
+    while True:
+        bVal = ser.read_until()
+        if len(bVal) == 0:
+            return
+
+def doVoltageSample(ser, voltage):
+    flushSerial(ser)
+    adcMedian = MedianAvg()
+    while True:
+        sLine = ser.read_until().decode('ascii')
+        if sLine.startswith('$ADC,') and sLine.endswith('\r\n'):
+            try:
+                iADC = int(sLine[5:-2])
+                #print(iADC)
+                adcMedian.add(iADC)
+                if len(adcMedian) >= 10:
+                    adcMedian.calc()
+                    print(f'{voltage:0.1f},{adcMedian.mean:0.4f},{adcMedian.min},{adcMedian.max}')
+                    adcMedian.reset()
+                    return
+            except ValueError:
+                pass
+
+def runSweep(args):
+    with serial.Serial(args.rport, baudrate=args.rbaud, timeout=0.010) as rcvr:
+        with KoradSerial(args.kport) as pwr:
+            try:
+                #print("Model: ", pwr.model)
+                pwrch = pwr.channels[0]
+                pwrch.voltage = 5.00
+                pwr.output.on()
+
+                print('voltage,mean,min,max')
+                for v in range(args.start, args.end+args.step, args.step):
+                    voltage = v / 100.0
+                    pwrch.voltage = voltage
+                    time.sleep(0.2)
+                    doVoltageSample(rcvr, voltage)
+            finally:
+                pwr.output.off()
+
+if __name__ == '__main__':
+    parser = argparse.ArgumentParser(
+        description="Run a voltage sweep using a Korad power supply and recevie ADC data from an ELRS receiver")
+    parser.add_argument("-b", "--rbaud", type=int, default=460800,
+        help="Receiver UART baud")
+    parser.add_argument("-e", "--end", type=int, default=100,
+        help="Ending voltage (centidegrees 500 = 5.00V)")
+    parser.add_argument("-k", "--kport", type=str, default='/dev/ttyACM0',
+        help="Port used for Korad power supply UART")
+    parser.add_argument("-r", "--rport", type=str, default='/dev/ttyUSB0',
+        help="Port used for receiver UART")
+    parser.add_argument("-s", "--start", type=int, default=3100,
+        help="Starting voltage (centidegrees 500 = 5.00V)")
+    parser.add_argument("-t", "--step", type=int, default=-10,
+        help="Voltage step (centidegrees -10 = -0.10V)")
+
+    args = parser.parse_args()
+
+    runSweep(args)
+

Original file line number	Diff line number	Diff line change
`@@ -32,5 +32,6 @@`
`32`	`32`	`"vbat": 34,`
`33`	`33`	`"vbat_offset": 12,`
`34`	`34`	`"vbat_scale": 410,`
	`35`	`+ "vbat_atten": 0,`
`35`	`36`	`"button": 0`
`36`	`37`	`}`