Frank Duignan / Mbed OS NRF52832_ML8511

This project can be used to measure UV light levels. It uses an ML8511 UV sensors and outputs its value over BLE in units of mW/cm^2

UVSensor.h@1:ab9f0e572c98, 2020-08-27 (annotated)

Committer:
f3d
Date:
Thu Aug 27 12:42:55 2020 +0000
Revision:
1:ab9f0e572c98
Initial commit

Who changed what in which revision?

UserRevisionLine numberNew contents of line
f3d 1:ab9f0e572c98 1 #ifndef __UVSENSOR_H
f3d 1:ab9f0e572c98 2 #define __UVSENSOR_H
f3d 1:ab9f0e572c98 3 #include <mbed.h>
f3d 1:ab9f0e572c98 4 #include <BLE.h>
f3d 1:ab9f0e572c98 5 AnalogIn UVSignalIn(P0_28);
f3d 1:ab9f0e572c98 6
f3d 1:ab9f0e572c98 7 class UVService {
f3d 1:ab9f0e572c98 8 public:
f3d 1:ab9f0e572c98 9 const static uint16_t UV_SERVICE_UUID = 0xA012;
f3d 1:ab9f0e572c98 10 const static uint16_t UV_CHARACTERISTIC_UUID = 0xA013;
f3d 1:ab9f0e572c98 11
f3d 1:ab9f0e572c98 12 UVService(BLE &_ble, int16_t initialUVValue) :
f3d 1:ab9f0e572c98 13 ble(_ble), UVValue(UV_CHARACTERISTIC_UUID, &initialUVValue)
f3d 1:ab9f0e572c98 14 {
f3d 1:ab9f0e572c98 15 GattCharacteristic *charTable[] = {&UVValue};
f3d 1:ab9f0e572c98 16 GattService uvservice(UV_SERVICE_UUID, charTable, sizeof(charTable) / sizeof(GattCharacteristic *));
f3d 1:ab9f0e572c98 17 ble.addService(uvservice);
f3d 1:ab9f0e572c98 18 }
f3d 1:ab9f0e572c98 19
f3d 1:ab9f0e572c98 20 GattAttribute::Handle_t getValueHandle() const {
f3d 1:ab9f0e572c98 21 return UVValue.getValueHandle();
f3d 1:ab9f0e572c98 22 }
f3d 1:ab9f0e572c98 23 void updateUVValue(uint16_t newValue) {
f3d 1:ab9f0e572c98 24 ble.gattServer().write(UVValue.getValueHandle(), (uint8_t *)&newValue, sizeof(uint16_t));
f3d 1:ab9f0e572c98 25 }
f3d 1:ab9f0e572c98 26
f3d 1:ab9f0e572c98 27 void poll()
f3d 1:ab9f0e572c98 28 {
f3d 1:ab9f0e572c98 29 uint16_t ADCIn = UVSignalIn.read_u16();
f3d 1:ab9f0e572c98 30 // Need to scale this to mW/cm^2
f3d 1:ab9f0e572c98 31 // To convert to a voltage : * 3.6/4095
f3d 1:ab9f0e572c98 32 // To convert voltage to mW/cm^2 see page 8 of datasheet for ML8511 sensor
f3d 1:ab9f0e572c98 33 // This graph is for 3.0V, but the supply in this example is 3.3V.
f3d 1:ab9f0e572c98 34 // I'm ASSUMING that the device output is not a function of voltage supply (within reason)
f3d 1:ab9f0e572c98 35 // From Graph : UV power / area is roughly given by:
f3d 1:ab9f0e572c98 36 // Power = (Voltage - 1) * 7;
f3d 1:ab9f0e572c98 37 // Need to avoid unsigned overflow
f3d 1:ab9f0e572c98 38 // An input of 1V should give an ADC Value of (1/3.6)*4095 = 1137.5 (1138)
f3d 1:ab9f0e572c98 39 if (ADCIn >= 1137 )
f3d 1:ab9f0e572c98 40 ADCIn = ADCIn - 1137;
f3d 1:ab9f0e572c98 41 else
f3d 1:ab9f0e572c98 42 ADCIn = 0;
f3d 1:ab9f0e572c98 43 ADCIn = ADCIn / 163; // 4095 / (7*3.6) = 163
f3d 1:ab9f0e572c98 44 updateUVValue(ADCIn);
f3d 1:ab9f0e572c98 45 }
f3d 1:ab9f0e572c98 46 private:
f3d 1:ab9f0e572c98 47 BLE &ble;
f3d 1:ab9f0e572c98 48 ReadOnlyGattCharacteristic<int16_t> UVValue;
f3d 1:ab9f0e572c98 49
f3d 1:ab9f0e572c98 50 };
f3d 1:ab9f0e572c98 51 #endif