FT4222H学习笔记7 - I2C Master
FT4222H的I2C支持I2C v2.1和v3版本。
【初始化函数】
[DllImport("LibFT4222.dll", CallingConvention = CallingConvention.Cdecl)]
public static extern eFT4222Status FT4222_I2CMaster_Init(IntPtr ftHandle, UInt32 kbps);
参数kbps的范围是60到3400，表示I2C的频率范围从60K到3.4M bps。
【写函数】
FT4222H读写函数分2类，基本型和扩展型，基本型是FT4222H的各个版本(A、B、C、D四个版本)都支持，扩展型A版本的芯片不支持。但是A版本已经没有了，所以基本只要了解扩张型的函数版本。
[DllImport("LibFT4222.dll", CallingConvention = CallingConvention.Cdecl)]
public static extern eFT4222Status FT4222_I2CMaster_WriteEx(
IntPtr ftHandle, UInt16 deviceAddress, byte flag, byte[] buffer, UInt16 bufferSize, ref UInt16 sizeTransferred);
参数deviceAddress是I2C从设备的地址，比如AT24C256的地址为0xA0，这个参数就是0x50；参数flag是定义一次写数据过程中的结构组成，有3个定义，分别为START = 0x02、REPEAT_START = 0x03、STOP = 0x04，如何一个数据过程中需要START和STOP，则Flag = 0x02 | 0x04；参数buffer是写入的数据；参数bufferSize是写入数据的长度；参数sizeTransferred是实际写入数据长度。
【读函数】
[DllImport("LibFT4222.dll", CallingConvention = CallingConvention.Cdecl)]
public static extern eFT4222Status FT4222_I2CMaster_ReadEx(
IntPtr ftHandle, UInt16 deviceAddress, byte flag, byte[] buffer, UInt16 bufferSize, ref UInt16 sizeTransferred);
参数的含义与写一样。
【获取状态】
[DllImport("LibFT4222.dll", CallingConvention = CallingConvention.Cdecl)]
public static extern eFT4222Status FT4222_I2CMaster_GetStatus(
IntPtr ftHandle, ref byte controllerStatus);
参数controllerStatus 是I2C控制的状态，每个bit的含义（为1时的含义）如下：
bit 0: 控制器忙，其他标志位无效。
bit 1: 错误条件
bit 2: 从属地址未响应
bit 3: 数据未响应
bit 4: 仲裁丢失
bit 5: 控制器空闲
bit 6: 总线忙
常用的I2C读写函数例程如下：
public static bool i2cRead(byte slaveAddr, byte addrbit, UInt16 addr, byte[] dat, UInt32 len)
{
UInt32 bufOffset = 0;
UInt16 count;
UInt16 maxSize = 60 * 1024;
bool result = true;
if (len == 0)
return result;
while (len > 0)
{
count = (len > maxSize) ? (UInt16)maxSize : (UInt16)len;
byte addrLen = (byte)((addrbit == 16) ? 2 : 1);
UInt16 index = 0;
byte[] addrBuf = new byte[addrLen];
if (addrbit == 16)
addrBuf[index++] = (byte)(addr >> 8);
addrBuf[index++] = (byte)(addr & 0xff);
ushort sizeTransferred = 0;
FT4222H.eFT4222Status ftStatus = 0;
ftStatus = FT4222H.FT4222_I2CMaster_WriteEx(i2cMHandle, slaveAddr, 0x02, addrBuf, addrLen, ref sizeTransferred);
if (ftStatus != FT4222H.eFT4222Status.FT4222_OK)
{
Console.WriteLine("I2CM read(wr addr) fail:" + ftStatus);
result = false;
break;
}
byte[] rdBuf = new byte[count];
ftStatus = FT4222H.FT4222_I2CMaster_ReadEx(i2cMHandle, slaveAddr, 0x03 | 0x04, rdBuf, count, ref sizeTransferred);
if (ftStatus != FT4222H.eFT4222Status.FT4222_OK)
{
Console.WriteLine("I2CM read fail:" + ftStatus);
result = false;
break;
}
Buffer.BlockCopy(rdBuf, 0, dat, (int)bufOffset, count);
bufOffset += count;
addr += count;
len -= count;
}
return result;
}
public static bool i2cWrite(byte slaveAddr, byte addrbit, UInt16 addr, byte[] dat, UInt32 len)
{
UInt32 bufOffset = 0;
UInt16 count;
UInt16 maxSize = 60 * 1024;
bool result = true;
if (len == 0)
return result;
while(len > 0)
{
count = (len > maxSize) ? (UInt16)maxSize : (UInt16)len;
byte addrLen = (byte)((addrbit == 16) ? 2 : 1);
UInt16 index = 0;
byte[] allBuf = new byte[count + addrLen];
if (addrbit == 16)
allBuf[index++] = (byte)(addr >> 8);
allBuf[index++] = (byte)(addr & 0xff);
Buffer.BlockCopy(dat, (int)bufOffset, allBuf, index, count);
ushort sizeTransferred = 0;
FT4222H.eFT4222Status ftStatus = 0;
ftStatus = FT4222H.FT4222_I2CMaster_WriteEx(i2cMHandle, slaveAddr, 0x06, allBuf, (UInt16)allBuf.Length, ref sizeTransferred);
if(ftStatus != FT4222H.eFT4222Status.FT4222_OK)
{
Console.WriteLine("I2CM Write fail:" + ftStatus);
result = false;
break;
}
do
{
byte controlStat = 0;
// to check if i2c progress succeed
FT4222H.FT4222_I2CMaster_GetStatus(i2cMHandle, ref controlStat);
if (controlStat == 0x20)
break;
if (FT4222H.eFT4222Status.FT4222_OK == ftStatus)
{
// is there any error occur
Console.WriteLine("I2CM Write status:" + controlStat);
if ((controlStat & 0x02) == 0x02)
{
// error happen
// reset i2c master to default
FT4222H.FT4222_I2CMaster_Reset(i2cMHandle);
result = false;
break;
}
}
else
{
// get status failed
result = false;
break;
}
} while (true);
if (result == false)
break;
bufOffset += count;
addr += count;
len -= count;
}
//
return result;
}
| Platform: FT4222H + AT24C256 |
||
| Clock(KHz) |
RD |
WR |
| 60 |
6315B |
395B |
| 100 |
10295B |
601B |
| 200 |
17904B |
964B |
| 400 |
34310B |
1448B |
| 1000 |
61706B |
1518B |
| 2000 |
1.2MB |
1575B |
| 3400 |
1.05MB |
1557B |
注：2M和4M的频率测试都失败，读回来的数据对不上。