// return: length of received data, or -1 for timeout
int SendDataTag(uint8_t *send, int sendlen, bool init, int speed, uint8_t *recv, uint16_t max_recv_len, uint32_t start_time, uint32_t *eof_time) {
// return: length of received data, or -1 for timeout
int SendDataTag(uint8_t *send, int sendlen, bool init, int speed, uint8_t *recv, uint16_t max_recv_len, uint32_t start_time, uint32_t *eof_time) {