Add Bluetooth examples

Co-authored-by: Peter Harper <77111776+peterharperuk@users.noreply.github.com>

pico_w/bt/standalone/server_common.c

@@ -0,0 +1,106 @@
+/**
+ * Copyright (c) 2023 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <stdio.h>
+#include "btstack.h"
+#include "hardware/adc.h"
+
+#include "temp_sensor.h"
+#include "server_common.h"
+
+#define APP_AD_FLAGS 0x06
+static uint8_t adv_data[] = {
+    // Flags general discoverable
+    0x02, BLUETOOTH_DATA_TYPE_FLAGS, APP_AD_FLAGS,
+    // Name
+    0x17, BLUETOOTH_DATA_TYPE_COMPLETE_LOCAL_NAME, 'P', 'i', 'c', 'o', ' ', '0', '0', ':', '0', '0', ':', '0', '0', ':', '0', '0', ':', '0', '0', ':', '0', '0',
+    0x03, BLUETOOTH_DATA_TYPE_COMPLETE_LIST_OF_16_BIT_SERVICE_CLASS_UUIDS, 0x1a, 0x18,
+};
+static const uint8_t adv_data_len = sizeof(adv_data);
+
+int le_notification_enabled;
+hci_con_handle_t con_handle;
+uint16_t current_temp;
+
+void packet_handler(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size) {
+    UNUSED(size);
+    UNUSED(channel);
+    bd_addr_t local_addr;
+    if (packet_type != HCI_EVENT_PACKET) return;
+
+    uint8_t event_type = hci_event_packet_get_type(packet);
+    switch(event_type){
+        case BTSTACK_EVENT_STATE:
+            if (btstack_event_state_get_state(packet) != HCI_STATE_WORKING) return;
+            gap_local_bd_addr(local_addr);
+            printf("BTstack up and running on %s.\n", bd_addr_to_str(local_addr));
+
+            // setup advertisements
+            uint16_t adv_int_min = 800;
+            uint16_t adv_int_max = 800;
+            uint8_t adv_type = 0;
+            bd_addr_t null_addr;
+            memset(null_addr, 0, 6);
+            gap_advertisements_set_params(adv_int_min, adv_int_max, adv_type, 0, null_addr, 0x07, 0x00);
+            assert(adv_data_len <= 31); // ble limitation
+            gap_advertisements_set_data(adv_data_len, (uint8_t*) adv_data);
+            gap_advertisements_enable(1);
+
+            poll_temp();
+
+            break;
+        case HCI_EVENT_DISCONNECTION_COMPLETE:
+            le_notification_enabled = 0;
+            break;
+        case ATT_EVENT_CAN_SEND_NOW:
+            att_server_notify(con_handle, ATT_CHARACTERISTIC_ORG_BLUETOOTH_CHARACTERISTIC_TEMPERATURE_01_VALUE_HANDLE, (uint8_t*)&current_temp, sizeof(current_temp));
+            break;
+        default:
+            break;
+    }
+}
+
+uint16_t att_read_callback(hci_con_handle_t connection_handle, uint16_t att_handle, uint16_t offset, uint8_t * buffer, uint16_t buffer_size) {
+    UNUSED(connection_handle);
+
+    if (att_handle == ATT_CHARACTERISTIC_ORG_BLUETOOTH_CHARACTERISTIC_TEMPERATURE_01_VALUE_HANDLE){
+        return att_read_callback_handle_blob((const uint8_t *)&current_temp, sizeof(current_temp), offset, buffer, buffer_size);
+    }
+    return 0;
+}
+
+int att_write_callback(hci_con_handle_t connection_handle, uint16_t att_handle, uint16_t transaction_mode, uint16_t offset, uint8_t *buffer, uint16_t buffer_size) {
+    UNUSED(transaction_mode);
+    UNUSED(offset);
+    UNUSED(buffer_size);
+    
+    if (att_handle != ATT_CHARACTERISTIC_ORG_BLUETOOTH_CHARACTERISTIC_TEMPERATURE_01_CLIENT_CONFIGURATION_HANDLE) return 0;
+    le_notification_enabled = little_endian_read_16(buffer, 0) == GATT_CLIENT_CHARACTERISTICS_CONFIGURATION_NOTIFICATION;
+    con_handle = connection_handle;
+    if (le_notification_enabled) {
+        att_server_request_can_send_now_event(con_handle);
+    }
+    return 0;
+}
+
+void poll_temp(void) {
+    adc_select_input(ADC_CHANNEL_TEMPSENSOR);
+    uint32_t raw32 = adc_read();
+    const uint32_t bits = 12;
+
+    // Scale raw reading to 16 bit value using a Taylor expansion (for 8 <= bits <= 16)
+    uint16_t raw16 = raw32 << (16 - bits) | raw32 >> (2 * bits - 16);
+
+    // ref https://github.com/raspberrypi/pico-micropython-examples/blob/master/adc/temperature.py
+    const float conversion_factor = 3.3 / (65535);
+    float reading = raw16 * conversion_factor;
+    
+    // The temperature sensor measures the Vbe voltage of a biased bipolar diode, connected to the fifth ADC channel
+    // Typically, Vbe = 0.706V at 27 degrees C, with a slope of -1.721mV (0.001721) per degree. 
+    float deg_c = 27 - (reading - 0.706) / 0.001721;
+    current_temp = deg_c * 100;
+    printf("Write temp %.2f degc\n", deg_c);
+ }