Using serial port with module xeno_16550A

["Zhao, Lixiang" <Lixiang.Zhao@leoni.com>]

Hello,

I'm currently porting xenomai on my project on a raspberry pi 4B and I would like some advice, I'm using xenomai 3.0.9 with a ipipe patch that I found on the web, I managed to set the module xeno_16550A and I was able to replace the default module that load ttyAMA0 of the pi to /dev/rtdm/rtser0. Beside this, I was able to adapt the code to the real time task with the Xenomai API, and the performance I get with each cyclic is really good.

I would like to use this file descriptor to perform some exchange, the simple test is to connect a Null cable on the RX/TX UART in order to form a loop. I did import the rtdm/serial.h, and explicitely call the __RT() functions on the open, write, read and ioctl on the low level functions. I am able to open the file, configure it with ioctl and the rtser_config struct, and writing on it. What I am struggling with is the read function, I am not able to retrieve the correct return value of the read, it always return -1, I'm not sure if my configuration is correct or not.

The rtser_config is the following :
    struct rtser_config my_config;

    my_config.config_mask       = 0xFFFF; // RTSER_SET_BAUD | RTSER_SET_TIMESTAMP_HISTORY; // //
    my_config.baud_rate         = 115200;
    my_config.parity            = RTSER_NO_PARITY;
    my_config.data_bits         = RTSER_8_BITS;
    my_config.stop_bits         = RTSER_2_STOPB;
    my_config.handshake         = RTSER_RTSCTS_HAND;
    my_config.fifo_depth        = RTSER_DEF_FIFO_DEPTH;
    my_config.rx_timeout        = RTDM_TIMEOUT_INFINITE;
    my_config.tx_timeout        = RTDM_TIMEOUT_INFINITE;
    my_config.event_timeout     = 1000000000; /* 1 s */
    my_config.timestamp_history = RTSER_RX_TIMESTAMP_HISTORY;
    my_config.event_mask        = RTSER_EVENT_RXPEND;
    my_config.rs485             = RTSER_RS485_DISABLE;

Could you help me on this issue ?

Best regards,
Li Xiang.