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PIC18F4550 MSSP I2C V.S MCP9801
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Level : 3 HP : 0 / 55 MP : 6 / 3198 EXP : 20
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請教版上的高手們,
目前手邊利用PIC18F4550 與MCP9801通訊,遇到一個問題~ 我是使用master mode ~ mcp9801 address 為000 //I2C 通訊初使化 OpenI2C(MASTER,SLEW_ON); SSPADD= 63; //baudrate 100KHz (Crystal :20MHz)
目前我設定mcp9801為12bit 解析,寫入動作ok,也得到slave ACK回應(由示波器上得知)~
問題出在於,當我要讀取2BYTES溫度資料時, 我使用 unsigned char Buf2[2]; union Byte2Int{ unsigned char A[2]; unsigned int B; } Temp;//Temp.B 為合併值
IdleI2C(); // ensure module is idle StartI2C();// Start condition I2C_Done(); WriteI2C(0x90); while(SSPCON2bits.ACKSTAT); I2C_Done();// Clear SSPIF flag WriteI2C(0x00);// 指定至溫度暫存器 while(SSPCON2bits.ACKSTAT); // wait until received the Acknowledge from MCP9801 I2C_Done(); RestartI2C(); //送出Restart訊號 I2C_Done(); WriteI2C(0x91); // 設定為讀出模式 while(SSPCON2bits.ACKSTAT); SSPCON2bits.ACKEN = 1; I2C_Done(); SSPCON2bits.RCEN = 1; getsI2C(Buf2,2); Temp.A[1] = Buf2[0]; Temp.A[0] = Buf2[1]; NotAckI2C(); I2C_Done(); StopI2C(); // Stop condition I2C_Done(); // Wait the Stop condition co return (Temp.B); //回傳12bits溫度值,放置在Temp.B Temp.B >> 4; Temp.B*0.0625 = 實際溫度
但目前我得到的溫度值並不正確(9801有回傳溫度資料),問題似乎是出現在I2C連續讀取2BYTES的格式寫法,請教版上的高手~用I2C連續讀取2BYTES的資料語法應為何??
發表於: 2009/2/21 2:06
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