概述： 我正在尝试使用 Ada Drivers Library 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 驱动程序库中最简单的 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”，然后一个“B”一直发送到“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。
【问题讨论】：
标签： ada bbc-microbit
我想通了。
让我们从两个 Arduino 程序开始，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 接收：
/*
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;
提示：
【讨论】：
我无法测试下面的代码，但它至少应该给你一些指导。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，您可能需要更改项目文件中microbit_zfp.gpr 的路径。
default.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;
main.adb
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;
【讨论】：
16#08# 是 8 十六进制（基数 16），即 8 十进制（基数 10）。 Arduino 必须是奴隶。但是请注意，Ctrl.Master_Receive 将等待传入字节。它不会发送请求。为此，您需要添加 Ctrl.Master_Transmit（请参阅更新的示例）。最后，原始示例使用 400 [kbps] 的默认速度设置，您可以在初始化期间更改此设置（请参阅microbit-i2c.ads 了解可用速度）。请再次注意，我无法对其进行测试（因为我目前没有 Arduino），所以这是最好的努力。
Data (0) 中的字节与可显示字符不对应，则Display (Character'Val (Data (0))); 将不起作用（即什么也不做）。
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。使用这两个文件构建应该更容易，但仍然无法构建，与 GPS 苦苦挣扎......我很快会再试一次......
【讨论】：