basic example code for Issue/324 on reading VSYS/VBUS while using wifi on Pico_W

pico_w/wifi_vsys/CMakeLists.txt

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+# Generated Cmake Pico project file
+
+cmake_minimum_required(VERSION 3.13)
+
+set(CMAKE_C_STANDARD 11)
+set(CMAKE_CXX_STANDARD 17)
+
+# Initialise pico_sdk from installed location
+# (note this can come from environment, CMake cache etc)
+set(PICO_SDK_PATH "/home/username/pico/pico-sdk")
+set(PICO_EXTRAS_PATH "/home/username/pico/pico-extras")
+
+set(PICO_BOARD pico_w CACHE STRING "Board type")
+
+# Pull in Raspberry Pi Pico SDK (must be before project)
+include(pico_sdk_import.cmake)
+include(${PICO_EXTRAS_PATH}/external/pico_extras_import.cmake)
+
+
+if (PICO_SDK_VERSION_STRING VERSION_LESS "1.4.0")
+  message(FATAL_ERROR "Raspberry Pi Pico SDK version 1.4.0 (or later) required. Your version is ${PICO_SDK_VERSION_STRING}")
+endif()
+
+project(wifi_vsys C CXX ASM)
+
+# Initialise the Raspberry Pi Pico SDK
+pico_sdk_init()
+
+# Add executable. Default name is the project name, version 0.1
+
+add_executable(wifi_vsys wifi_vsys.cpp )
+
+pico_set_program_name(wifi_vsys "wifi_vsys")
+pico_set_program_version(wifi_vsys "0.1")
+
+pico_enable_stdio_uart(wifi_vsys 0)
+pico_enable_stdio_usb(wifi_vsys 1)
+
+# Add the standard library to the build
+target_link_libraries(wifi_vsys
+        pico_stdlib
+        pico_lwip_http
+        pico_cyw43_arch_lwip_threadsafe_background
+        hardware_adc
+        )
+
+# Add the standard include files to the build
+target_include_directories(wifi_vsys PRIVATE
+  ${CMAKE_CURRENT_LIST_DIR}
+  ${CMAKE_CURRENT_LIST_DIR}/.. # for our common lwipopts or any other standard includes, if required
+)
+
+pico_add_extra_outputs(wifi_vsys)

pico_w/wifi_vsys/lwipopts.h

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+#ifndef _LWIPOPTS_H
+#define _LWIPOPTS_H
+
+// Generally you would define your own explicit list of lwIP options
+// (see https://www.nongnu.org/lwip/2_1_x/group__lwip__opts.html)
+//
+// This example uses a common include to avoid repetition
+#include "lwipopts_examples_common.h"
+
+#endif

pico_w/wifi_vsys/wifi_vsys.cpp

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+#include <stdio.h>
+#include "pico/stdlib.h"
+#include "pico/cyw43_arch.h"
+#include "hardware/gpio.h"
+#include "hardware/adc.h"           //to read ADC for soil moisture sensor, connected to pin 36 (3.3V), pin 33 (GND/AGND), pin 34 (GPIO28/ADC2)
+#include "lwip/apps/http_client.h"  //http client
+#include "pico/cyw43_arch/arch_threadsafe_background.h"  //to get access to void cyw43_thread_enter(void);  and void cyw43_thread_exit(void);
+
+#ifndef CYW43_WL_GPIO2
+#define CYW43_WL_GPIO2 2  //this is not defined in pico_w.h
+#endif
+
+const float conversion_factor = 3.3f / (1 << 12); //ADC_VREF=3.3, so this is the ADC resolution. 
+const char ssid[] = "myWifiNetwork";
+const char pass[] = "myWifiPassword";
+const uint32_t auth = CYW43_AUTH_WPA2_MIXED_PSK;
+
+//Http client variables
+bool httpBusy = false;
+char httpBuff[1000]; //if not big enough to read the result or headers, pico will hang.
+httpc_connection_t settings;
+ip_addr_t ip;
+char apicall[64];
+
+
+//handler for HTTP client result
+void httpresult(void *arg, httpc_result_t httpc_result, u32_t rx_content_len, u32_t srv_res, err_t err)
+{
+    printf("[1] local result=%d  http result=%d\n", httpc_result, srv_res);
+}
+
+//handler for HTTP client headers
+err_t headers(httpc_state_t *connection, void *arg, struct pbuf *hdr, u16_t hdr_len, u32_t content_len)
+{
+    pbuf_copy_partial(hdr, httpBuff, hdr->tot_len, 0);
+    printf("[1] content length=%d,  header length %d, headers: %s\n", content_len, hdr_len, httpBuff);
+    //free memory
+	pbuf_free(hdr); 
+    return ERR_OK;
+}
+
+//handler for HTTP client body
+err_t body(void *arg, struct altcp_pcb *conn, struct pbuf *p, err_t err)
+{
+    pbuf_copy_partial(p, httpBuff, p->tot_len, 0);
+    printf("[1] body: %s", httpBuff);
+    httpBusy = false;
+    //free memory 
+    pbuf_free(p);
+    return ERR_OK;
+}
+
+//Set GPIO29 back to settings for wifi usage (shared pin with ADC3, so settings are changed when activating ADC3)
+void SetGPIO29WifiStatus()
+{
+    gpio_set_function(29, GPIO_FUNC_PIO1); //7
+    gpio_pull_down(29);
+    gpio_set_slew_rate(29, GPIO_SLEW_RATE_FAST); //1
+    gpio_set_drive_strength(29, GPIO_DRIVE_STRENGTH_12MA); //3
+}
+
+int main() {
+    stdio_init_all();
+    adc_init();
+    adc_gpio_init(28);
+
+    //Initialize wifi
+    if (cyw43_arch_init()) {
+        printf("WiFi init failed.\n");
+        return 1;
+    }
+    cyw43_arch_enable_sta_mode();
+    //connect to access point
+    if (cyw43_arch_wifi_connect_timeout_ms(ssid, pass, auth, 30000)) {
+        printf("failed to connect.\n");
+        return 1;
+    } else {
+        printf("Connected.\n");
+    }
+
+    //set http client handlers
+    settings.result_fn = httpresult;
+    settings.headers_done_fn = headers;   
+    //define IP address that hosts the web api to send the data
+    IP4_ADDR(&ip, 192, 168, 0, 1);
+    int ledStatus = 0;
+    float vsys=0;
+
+    while(true) {        
+        //flip onboard led
+        ledStatus = 1 - ledStatus;
+        cyw43_arch_gpio_put(CYW43_WL_GPIO_LED_PIN, ledStatus);
+
+        //Select ADC2 to read moisture sensor
+        adc_select_input(2);
+        uint16_t result = adc_read();
+        float voltage = result * conversion_factor;
+        printf("ADC2 value: 0x%03x, %i, voltage: %3.1f V\n", result, result, voltage);
+
+        //make sure there is not HTTP request in progress or other wifi activity when we want to check the battery status    
+        if (!httpBusy){            
+            httpBusy = true;
+
+            //prevent wifi background processing so we can use the shared pins
+            cyw43_thread_enter();   //or macro: CYW43_THREAD_ENTER
+
+            //WL_GPIO2, IP VBUS sense - high if VBUS is present, else low
+            uint vbus = cyw43_arch_gpio_get(CYW43_WL_GPIO2); 
+
+            //we could decide to only check the voltage if not powered by USB port/VBUS and perhaps not check it every cycle.
+            //if (vbus==0)            
+            //{
+            //initialize and select ADC3/GPIO29                
+            adc_gpio_init(29);
+            adc_select_input(3);
+
+            //Read ADC3, result is 1/3 of VSYS, so we still need to multiply the conversion factor with 3 to get the input voltage
+            uint16_t adc3 = adc_read();
+            vsys = adc3 * conversion_factor * 3; 
+            printf("ADC3 value: 0x%03x, %i, voltage: %f V\n", adc3, adc3, vsys);
+            //set GPIO29 back to the settings for wifi, otherwise cyw43 will not work correctly
+            SetGPIO29WifiStatus();
+            //}
+            //else{                
+                //USB/VSYS powered, do nothing (voltage should be somewhere around 5V)
+            //}
+            //exit to allow wifi communication again
+            cyw43_thread_exit();    //or macro: CYW43_THREAD_EXIT
+
+            sprintf(apicall, "/api/echo?m=%3.3f&v=%3.3f&b=%i", voltage, vsys, vbus);
+            printf("Calling API: %s\n", apicall);
+            err_t err = httpc_get_file(
+                &ip,        //IP address hosting the API
+                5131,       //port
+                apicall,    //api call
+                &settings,  //handlers for result/headers
+                body,       //handler for body
+                NULL,
+                NULL
+            );  
+            printf("[1] http status %d \n", err);
+        }
+        else{
+            printf("[1] http client is busy...\n");
+        }
+
+#if PICO_CYW43_ARCH_POLL
+        // if you are using pico_cyw43_arch_poll, then you must poll periodically from your
+        // main loop (not from a timer) to check for WiFi driver or lwIP work that needs to be done.
+        cyw43_arch_poll();
+        sleep_ms(1);
+#else
+        // if you are not using pico_cyw43_arch_poll, then WiFI driver and lwIP work
+        // is done via interrupt in the background. This sleep is just an example of some (blocking)
+        // work you might be doing.
+       sleep_ms(5000);        
+#endif        
+    }
+
+    cyw43_arch_deinit();
+    return 0;
+}