Using a second UART to control a serial device

Reinier Millo Sánchez rmillo at uclv.cu
Sat Apr 18 16:17:03 CEST 2015


Hi Clemens

I have been testing something similar in other board (YSE5250-Exynos5). 
First you must guarantee that the UART device driver is compatible with 
the hardware or you must write an specific device driver.
I have tried to make a GPS device driver using the S3C2410 UART based on 
the serial-drv package.
To connect the uart on the user land with my server i have configured 
the HW.Device in a vbus with the IO server using this configuration:

    -- File: yse5250.devs

    local Hw = Io.Hw
    local Res = Io.Res
    Io.hw_add_devices
    {
    UART3 = Hw.Device
    {
    hid = "UART3";
    Res.irq(86);
    Res.mmio(0x12C30000, 0x12C3ffff);
    }
    }

To create the vbus, i have created the file yse5250.io:

    -- File: yse5250.io

    Io.add_vbusses
    {
    -- Create a virtual bus for a client and give access to UART3
    uart03 = Io.Vi.System_bus(function ()
    dev = wrap(Io.system_bus():match("UART3"));
    end);
    }

To run my server using the UART3 on the vbus have used this configuration

    -- gps-drv.cfg

    -- Run GPS Driver for YSE5250 (Exynos 5250)
    require("L4");
    -- Shortcuts
    local ld = L4.default_loader;
    local vbus_uart03 = ld:new_channel();
    local platform_ctl = ld:new_channel();
    local gps_srv = ld:new_channel();
    -- Start the IO Server
    ld:start(
    {
    caps = {
    sigma0 = L4.cast(L4.Proto.Factory,
    L4.Env.sigma0):create(L4.Proto.Sigma0);
    icu = L4.Env.icu;
    platform_ctl = platform_ctl:svr();
    uart03 = vbus_uart03:svr();
    },
    log = { "IO Server", "green" },
    l4re_dbg = L4.Dbg.Warn,
    }, "rom/io rom/yse5250.devs rom/yse5250.io");
    -- Start the GPS Driver Server conected to UART3
    ld:start(
    {
    caps = {
    gps_srv = gps_srv:svr();
    vbus = vbus_uart03;
    },
    log = {"GPS Driver","blue"}
    }, "rom/gps_drv");

The server code is very similar to:

/pkg/serial-drv/server/src/main.cc

But in my case i have adjusted the UART to use the S3C2410 uart.

Best regards


On 04/18/2015 06:00 AM, l4-hackers-request at os.inf.tu-dresden.de wrote:
> Message: 1
> Date: Fri, 17 Apr 2015 12:03:46 +0200
> From: "Pflaum, Clemens"<clemens.pflaum at mytum.de>
> To:l4-hackers at os.inf.tu-dresden.de
> Subject: Using a second UART to control a serial device
> Message-ID:<4a79357eec3b3359e8b09e16a3fe0994 at roundcube.lrz.de>
> Content-Type: text/plain; charset=US-ASCII; format=flowed
>
> Hi L4 Hackers,
> Im currently running Fiasco.OC with L4Re on my BananaPi. I'm trying to
> control a serial device (Pololu Servo Controller) by sending a small
> series of Bytes over a second UART ( not UART 0 since im getting the
> console from there ). Via documentation I've found out that UART 3 is at
> 0x01C28C00 and is a U6_16550A, so I'm hoping the driver  in
> /pkg/drivers-frst/uart/src/uart_pxa.cc will be compatible with that.
> Where and how would I have to go about initiating my UART 3? By writing
> a new platform for BPi in /pkg/bootstrap/server/src/platform? The
> function set_stdio_uart(&_uart); made me think its only the "console"
> UART. Or do I have to instantiate some kind of Hw.Device like the gpio
> in /pkg/io/config/arm-omap3.devs and put it on a new vBus like in
> /pkg/io/doc/example.io ?
>
> Or am I thinking way too complicated and it is as simple as editing the
> /pkg/serial-drv/server/src/main.cc :
>
> bool
> Serial_drv::init()
> {
>     int irq_num = 37;
>           // How can i find out what this number refers to/do i have to
> change it at all?
>     l4_addr_t phys_base = 0x1000a000;
>           // change to 0x01C28C00
> #if 0
>     int irq_num = 74;
>     l4_addr_t phys_base = 0x49020000;
> #endif
>     l4_addr_t virt_base = 0;
>
>     if (l4io_request_iomem(phys_base, 0x1000, L4IO_MEM_NONCACHED,
> &virt_base))
>       {
>         printf("serial-drv: request io-memory from l4io failed.\n");
>         return false;
>       }
>     printf("serial-drv: virtual base at:%lx\n", virt_base);
>
>     L4::Io_register_block_mmio *regs = new
> L4::Io_register_block_mmio(virt_base);
>     _uart = new (malloc(sizeof(L4::Uart_pl011))) L4::Uart_pl011(24019200);
>                      //change to L4::Uart_pxa(what does this number mean?)
>     _uart->startup(regs);
>
>
> Thanks for any answers in advance.
>
> Regards,
> Clemensc... at mytum.de

-- 
Lic. Reinier Millo Sánchez
Centro de Estudios de Informática
Universidad Central "Marta Abreu" de Las Villas
Carretera a Camajuaní Km 5 1/2
Santa Clara, Villa Clara, Cuba
CP 54830

"antes de discutir ... respira;
   antes de hablar ... escucha;
  antes de escribir ... piensa;
   antes de herir ... siente;
  antes de rendirte ... intenta;
   antes de morir ... vive"

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