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概述： 我正在尝试使用 Ada 驱动程序库使用 Ada 对 microbit 进行编程，但我不明白如何使用 i2c 功能与另一个芯片建立通信。我想建立一个简单的演示，这样我就可以理解发生了什么，因为 Ada 驱动程序库的组件目录中的演示超出了我的想象（我对 Ada 也很陌生，这无济于事）。

Ada Drivers Library 中最简单的 i2c 演示似乎适用于 AK8963 三轴罗盘（位于 /components/src/motion/ak8963/）。但这仍然让我头疼，而且我没有芯片来运行和调试代码。

这是我尝试过的： 我用 arduinos 创建了两个不同的演示。在这两个演示中，发射器发送一个“A”，然后发送一个“B”一直到“Z”，然后循环回到“A”。在第一个演示中，主机每 500 毫秒发送下一个字符，从机接收它。在第二个演示中，主机每 500 毫秒请求下一个字符，从机发送它。

我的演示改编自此处和此处的 arduino Wire 示例。

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3 回答 3

2

我想到了。

让我们从两个 Arduino 程序开始，以证明 Arduino 代码有效。

Arduino Slave 传输：

/*
Sends the next letter of the alphabet with each
request for data from master.

Watch the serial monitor to see what's happening.
*/

#include <avr/wdt.h>
#include <Wire.h>

// A note about I2C addresses.
// The Ada program is looking for the slave on address 16
// but this code says the slave is on 8.
// What's happening? As best as I can tell it works
// like this:
// 16 in binary is 10000. But arduino strips the read/write bit 
// (which is the last bit) off of the address so it becomes 
// 1000 in binary. And 1000 in binary is 8.
const int SLAVE_ADDRESS = 8;
byte letter = 65; // letter A
unsigned long counter = 0;

void setup()
{
  wdt_reset();
  wdt_enable(WDTO_8S);

  Serial.begin(9600);
  Serial.println("beginning");

  Wire.begin(SLAVE_ADDRESS);        // join i2c bus
  Wire.onRequest(requestEvent);     // register event
}

void loop()
{
  wdt_reset();
  counter++;
  if(counter % 1000 == 0)
  {
    // Display a heart beat so we know the arduino has not hung.
    Serial.print("looping: ");
    Serial.println(counter);
  }
  delay(5);
}

// function that executes whenever data is requested by master
// this function is registered as an event, see setup()
void requestEvent()
{
  // send the current letter on I2C
  Wire.write(letter);

  Serial.print("transmitting: ");
  Serial.println(char(letter));

  letter++;
  if(letter > 90) // if greater than Z
  {
    letter = 65; // reset to A
  }
}

Arduino Master 收到：

/*
Requests a character from the slave every 500 ms and prints it
to the serial monitor.
*/

#include <avr/wdt.h>
#include <Wire.h>

const int SLAVE_ADDRESS = 8;

void setup()
{
  wdt_reset();
  wdt_enable(WDTO_8S);
  Wire.begin();        // join i2c bus
  Serial.begin(9600);
}

void loop()
{
  // reset the watchdog timer
  wdt_reset();

  // request one byte from the slave
  Wire.requestFrom(SLAVE_ADDRESS, 1);

  while(Wire.available()) // slave may send less than requested
  {
      // receive a byte as character
    char c = Wire.read();
    Serial.println(c);
  }
  delay(500);
}

这两个 Arduino 草图将愉快地传递字符一整天。现在用下面的 Ada 版本替换 Arduino 主接收器，并物理断开 Arduino 主接收器。

Ada 主接收器（main.abd）：

--  Request a character from the I2C slave and
--  display it on the 5x5 display in a loop.

with HAL.I2C;          use HAL.I2C;
with MicroBit.Display; use MicroBit.Display;
with MicroBit.I2C;
with MicroBit.Time;

procedure Main is
   Ctrl   : constant Any_I2C_Port := MicroBit.I2C.Controller;
   Addr   : constant I2C_Address := 16;
   Data   : I2C_Data (0 .. 0);
   Status : I2C_Status;
begin

   MicroBit.I2C.Initialize (MicroBit.I2C.S100kbps);
   if MicroBit.I2C.Initialized then
      --  Successfully initialized I2C
      Display ('I');  
   else
      --  Error initializing I2C
      Display ('E');  
   end if;
   MicroBit.Time.Delay_Ms (2000);
   MicroBit.Display.Clear;

   loop
      --  Request a character
      Ctrl.Master_Receive (Addr => Addr, Data => Data, Status => Status);

      --  Display the character or the error
      if Status = Ok then
         Display (Character'Val (Data (0)));
      else
         MicroBit.Display.Display (Status'Image);
      end if;

      --  Give the user time to read the display
      MicroBit.Time.Delay_Ms (1000);
      MicroBit.Display.Clear;
      MicroBit.Time.Delay_Ms (250);
   end loop;
end Main;

为了完整起见，这里是 Ada 项目文件：

with "..\..\Ada_Drivers_Library\boards\MicroBit\microbit_zfp.gpr";

project I2C_Master_Receive_Demo is

   for Runtime ("ada") use Microbit_Zfp'Runtime ("Ada");
   for Target use "arm-eabi";
   for Main use ("main.adb");
   for Languages use ("Ada");
   for Source_Dirs use ("src");
   for Object_Dir use "obj";
   for Create_Missing_Dirs use "True";

   package Compiler renames Microbit_Zfp.Compiler;

   package Linker is
      for Default_Switches ("ada") use Microbit_Zfp.Linker_Switches & ("-Wl,--print-memory-usage", "-Wl,--gc-sections", "-U__gnat_irq_trap");
   end Linker;

   package Ide is
      for Program_Host use ":1234";
      for Communication_Protocol use "remote";
      for Connection_Tool use "pyocd";
   end Ide;

end I2C_Master_Receive_Demo;

尖端：

  • 您需要观察 I2C 地址偏移量（在我的例子中，Ada 中的 16 = Arduino 上的 8）。请参阅上面从属传输 arduino 代码的注释中的解释。我花了很长时间才弄清楚这一点。
  • 连接到 I2C 总线的三个设备没有任何工作，即使其中一个没有通电。我不确切知道那里发生了什么，但我怀疑它与说明 I2C 总线无法将其线路拉回高电平的文档有关。一些文档建议在连接到源电压的两条 I2C 线路上放置一个电阻器，以便线路电压在设备将其拉低后返回到高电平。
  • 使用示波器，这项工作会更容易。如果我有一个问题，我可以更快地解决这个问题。
于 2019-10-19T17:03:48.990 回答
0

我无法测试下面的代码，但它至少应该给你一些方向。请注意，micro:bit 充当主机。我不认为 micro:bit 可以在 I2C 总线上充当从设备（但我在这里可能错了）。另请注意，您可能必须更改microbit_zfp.gpr项目文件中的路径。

默认.gpr

with "../Ada_Drivers_Library/boards/MicroBit/microbit_zfp.gpr";

project Default is

  for Runtime ("ada")      use MicroBit_ZFP'Runtime ("Ada");
  for Target               use "arm-eabi";
  for Main                 use ("main.adb");
  for Languages            use ("Ada");
  for Source_Dirs          use ("src");
  for Object_Dir           use "obj";
  for Create_Missing_Dirs  use "True";

  package Compiler renames MicroBit_ZFP.Compiler;

  package Linker is
     for Default_Switches ("Ada") use
       MicroBit_ZFP.Linker_Switches &
       ("-Wl,--print-memory-usage",
        "-Wl,--gc-sections",
        "-U__gnat_irq_trap");
  end Linker;

end Default;

主文件

with MicroBit.Display; use MicroBit.Display;
with MicroBit.Time;    use MicroBit.Time;
with MicroBit.I2C;     use MicroBit.I2C;
with HAL.I2C;          use HAL.I2C;

procedure Main is
begin

   MicroBit.I2C.Initialize (S400kbps);   --  Change to desired speed.

   declare    
      Ctrl   : constant Any_I2C_Port := MicroBit.I2C.Controller;
      Addr   : constant I2C_Address := 16#08#;    --  Change to correct address.
      Data   : I2C_Data (0 .. 0);
      Status : I2C_Status;
   begin
      loop

         --  Data to be send (here: character 'x').
         Data (0) := Character'Pos ('x');

         --  Display a dot to indicate where we are.
         Display ('.');

         --  Send 1 byte of data (length of Data array is 1).
         Ctrl.Master_Transmit (Addr, Data, Status);

         --  Additional status checking could be done here....

         --  Display a colon to indicate where we are.
         Display (':');

         --  Wait for response (1 byte as the length of the Data array is 1).         
         Ctrl.Master_Receive (Addr, Data, Status);

         --  Check status, and display character if OK.
         if Status = Ok then
            Display (Character'Val (Data (0)));
         else
            Display ('!');
         end if;

         -- Take a short nap (time in milliseconds).
         Sleep (250);

      end loop;
   end;

end Main;
于 2019-10-09T14:06:04.847 回答
0

我目前对 BBC micro:bit 和 i2c 感兴趣，并尝试了该程序，之前有一个程序可以成功构建和上传。用这两个文件构建应该更容易，仍然没有构建它，与 GPS 苦苦挣扎......我会很快再试一次......

于 2019-10-16T23:34:47.987 回答