Bluetooth chip doesn't work on UART3 interface

[lihing1994]

I am trying to bring up the WL1837 Wi-Fi + Bluetooth chip on the MA35D1 platform. According to the datasheet, the Bluetooth interface requires hardware flow control (RTS/CTS). It seems like the handshaking between UART and WL1837 is failed. Thanks in advance for any hint and help for solving this issue!

Steps Taken:

• Verified the physical connection between the CTS and RTS pins on the SoC and the WL1837 module.
• Enabled uart-has-rtscts; in the uart3 device tree node to enable hardware flow control.
• Tried to add small delay before the handshake is being built.(this commit)
  Despite these changes, the Bluetooth chip fails during the probe process.

Here is the potion of kernel dmesg that related to the Bluetooth.

root@som-35d1f:~# dmesg | grep Blue
[    0.720442] Bluetooth: Core ver 2.22
[    0.728375] Bluetooth: HCI device and connection manager initialized
[    0.734708] Bluetooth: HCI socket layer initialized
[    0.739555] Bluetooth: L2CAP socket layer initialized
[    0.744596] Bluetooth: SCO socket layer initialized
[    2.442381] Bluetooth: HCI UART driver ver 2.3
[    2.446779] Bluetooth: HCI UART protocol H4 registered
[    2.451873] Bluetooth: HCI UART protocol BCSP registered
[    2.452029] Bluetooth: HCI UART protocol LL registered
[    2.464097] Bluetooth: HCI UART protocol ATH3K registered
[    2.464145] Bluetooth: HCI UART protocol Three-wire (H5) registered
[    4.775363] Bluetooth: hci0: command 0x1001 tx timeout
[    5.537772] Bluetooth: RFCOMM TTY layer initialized
[    5.542638] Bluetooth: RFCOMM socket layer initialized
[    5.547730] Bluetooth: RFCOMM ver 1.11
[    5.551439] Bluetooth: BNEP (Ethernet Emulation) ver 1.3
[    5.556712] Bluetooth: BNEP filters: protocol multicast
[    5.561919] Bluetooth: BNEP socket layer initialized
[    5.566852] Bluetooth: HIDP (Human Interface Emulation) ver 1.2
[    5.572751] Bluetooth: HIDP socket layer initialized
[   13.223357] Bluetooth: hci0: Reading TI version information failed (-110)
[   13.230108] Bluetooth: hci0: download firmware failed, retrying...
[   15.463352] Bluetooth: hci0: command 0x1001 tx timeout
[   23.463352] Bluetooth: hci0: Reading TI version information failed (-110)
[   23.463372] Bluetooth: hci0: download firmware failed, retrying...
[   25.703334] Bluetooth: hci0: command 0x1001 tx timeout
[   33.703350] Bluetooth: hci0: Reading TI version information failed (-110)
[   33.703368] Bluetooth: hci0: download firmware failed, retrying...
[   35.943336] Bluetooth: hci0: command 0x1001 tx timeout
[   43.943359] Bluetooth: hci0: Reading TI version information failed (-110)
[   43.943379] Bluetooth: hci0: download firmware failed, retrying...
root@som-35d1f:~#

Here is the potion of device tree that related to the Bluetooth.

&uart3 {
        /* uart3 interface is being utilized for Bluetooth functionality */
        status = "okay";
        pinctrl-names = "default";
        pinctrl-0 = <&pinctrl_wl1837_bt>;
        /*  uart-has-rtscts; */
        bluetooth {
                compatible = "ti,wl1837-st";
                enable-gpios = <&gpio_expander_on_som 2 GPIO_ACTIVE_HIGH>;
                vio-supply = <&general_1v8_regulator>;
                vbat-supply = <&general_3v3_regulator>;
        };
};

&pinctrl {
      bt {
                pinctrl_wl1837_bt: wl1837_btgrp{
                        nuvoton,pins =
                                <SYS_GPA_MFPL_PA4MFP_UART3_nCTS     &pcfg_default>,
                                <SYS_GPA_MFPL_PA5MFP_UART3_nRTS     &pcfg_default>,
                                <SYS_GPA_MFPL_PA6MFP_UART3_RXD      &pcfg_default>,
                                <SYS_GPA_MFPL_PA7MFP_UART3_TXD      &pcfg_default>;
                };
        };
};

[mjchen1]

You can use the following setting in the application code:
options.c_cflag |= CRTSCTS;

[lihing1994]

You can use the following setting in the application code:
options.c_cflag |= CRTSCTS;

Any chance you can elaborate on this? You meaning adding this in TI HCI_LL.c driver code? Thanks!

[mjchen1]

Here is a simple example of setting up UART:

int main() {
int serial_fd;
struct termios options;

serial_fd = open("/dev/ttyS0", O_RDWR | O_NOCTTY | O_NDELAY);
if (serial_fd == -1) {
    perror("Unable to open UART");
    return -1;
}

tcgetattr(serial_fd, &options);

cfsetispeed(&options, B115200); 
cfsetospeed(&options, B115200); 

// Enable Flow control
options.c_cflag |= CRTSCTS;

options.c_cflag &= ~PARENB;
options.c_cflag &= ~CSTOPB;
options.c_cflag &= ~CSIZE;
options.c_cflag |= CS8;

options.c_cflag |= CREAD | CLOCAL;

tcsetattr(serial_fd, TCSANOW, &options);

write(serial_fd, "Hello UART with flow control!\n", 30);

close(serial_fd);

return 0;

}

[lihing1994]

Here is a simple example of setting up UART:

int main() {
int serial_fd;
struct termios options;

serial_fd = open("/dev/ttyS0", O_RDWR | O_NOCTTY | O_NDELAY);
if (serial_fd == -1) {
    perror("Unable to open UART");
    return -1;
}

tcgetattr(serial_fd, &options);

cfsetispeed(&options, B115200); 
cfsetospeed(&options, B115200); 

// Enable Flow control
options.c_cflag |= CRTSCTS;

options.c_cflag &= ~PARENB;
options.c_cflag &= ~CSTOPB;
options.c_cflag &= ~CSIZE;
options.c_cflag |= CS8;

options.c_cflag |= CREAD | CLOCAL;

tcsetattr(serial_fd, TCSANOW, &options);

write(serial_fd, "Hello UART with flow control!\n", 30);

close(serial_fd);

return 0;

}

• I’m not entirely sure why I need to use this code to set up the UART. It appears the dmesg I attached above saying that the Bluetooth driver fails during the initialization process. Shouldn’t I focus on identifying the issue causing the driver to fail to communicate with the UART controller instead?

[mjchen1]

From the beginning, I thought you were asking about how to set up CTS/RTS, but it seems that’s not the case. You might need to first confirm whether the UART signals are being transmitted correctly and whether the CTS/RTS actions are functioning properly.