Example app demonstrating how to stream accelerometer data using AppMessage callbacks. To do this, accelerometer data is gathered via the AccelDataService:
static void accel_data_handler(AccelData *data, uint32_t num_samples) {
// ...
send(data, num_samples);
// ...
}
Each set of samples received is transmitted to the Android app for display via AppMessage:
static void send(AccelData *data, uint32_t num_samples) {
if(comm_send_data(data, num_samples)) {
// ...
}
}
bool comm_send_data(AccelData *data, uint32_t num_samples) {
DictionaryIterator *out;
AppMessageResult result = app_message_outbox_begin(&out);
if(result == APP_MSG_OK) {
for(uint32_t i = 0; i < num_samples; i++) {
dict_write_int16(out, (COMM_NUM_PACKET_ELEMENTS * i) + 0, data[i].x);
dict_write_int16(out, (COMM_NUM_PACKET_ELEMENTS * i) + 1, data[i].y);
dict_write_int16(out, (COMM_NUM_PACKET_ELEMENTS * i) + 2, data[i].z);
}
if(app_message_outbox_send() == APP_MSG_OK) {
s_busy = true;
return true;
}
// ...
}
}
The availability of the channel is tracked using AppMessage callbacks to prevent transmission attempts before the previous packet has been acknowledged.
static void outbox_sent_handler(DictionaryIterator *iterator, void *context) {
// Message acknowledged, no longer busy
s_busy = false;
}
if(comm_is_busy()) {
APP_LOG(APP_LOG_LEVEL_WARNING, "Accel sample arrived early");
window_set_background_color(s_window, GColorRed);
} else {
send(data, num_samples);
}