Added analog class for plasma current reading

drivers/CMakeLists.txt

@@ -1,3 +1,4 @@
+add_subdirectory(analog)
 add_subdirectory(esp32spi)
 add_subdirectory(ioexpander)
 add_subdirectory(ltp305)

drivers/analog/CMakeLists.txt

@@ -0,0 +1 @@
+include(analog.cmake)

drivers/analog/analog.cmake

@@ -0,0 +1,11 @@
+set(DRIVER_NAME analog)
+add_library(${DRIVER_NAME} INTERFACE)
+
+target_sources(${DRIVER_NAME} INTERFACE
+  ${CMAKE_CURRENT_LIST_DIR}/${DRIVER_NAME}.cpp
+)
+
+target_include_directories(${DRIVER_NAME} INTERFACE ${CMAKE_CURRENT_LIST_DIR})
+
+# Pull in pico libraries that we need
+target_link_libraries(${DRIVER_NAME} INTERFACE pico_stdlib hardware_adc)

drivers/analog/analog.cpp

@@ -0,0 +1,18 @@
+#include "analog.hpp"
+
+namespace pimoroni {
+    uint16_t Analog::read_raw() {
+      return adc_read();
+    }
+
+    float Analog::read_voltage() {
+      return ((float)adc_read() * 3.3f) / (1 << 12) / amplifier_gain;
+    }
+
+    float Analog::read_current() {
+      if(resistor > 0.0f)
+        return read_voltage() / resistor;
+      else
+        return read_voltage();
+    }
+};

drivers/analog/analog.hpp

@@ -0,0 +1,31 @@
+#pragma once
+
+#include <stdint.h>
+#include "pico/stdlib.h"
+#include "hardware/adc.h"
+#include "common/pimoroni_common.hpp"
+
+namespace pimoroni {
+
+  class Analog {
+  public:
+    Analog(uint pin, float amplifier_gain = 1.0f, float resistor = 0.0f) :
+    pin(pin), amplifier_gain(amplifier_gain), resistor(resistor) {
+      adc_init();
+
+      //Make sure GPIO is high-impedance, no pullups etc
+      adc_gpio_init(pin);
+
+      //Select ADC input 0 (GPIO26)
+      adc_select_input(pin - 26);
+    };
+    uint16_t read_raw();
+    float read_voltage();
+    float read_current();
+  private:
+    uint pin;
+    float amplifier_gain;
+    float resistor;
+  };
+
+}