FPGA與DHT11串列通訊
使用VHDL硬體描述語言撰寫的串列通訊韌體來讀取DHT11感測到的溫濕度數據。
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前言
當初因為被選上了工科技藝競賽數位電子組的選手，所以開始了VHDL的培訓。經過了兩個月的基本語法培訓後，我開始嘗試去看原模組datasheet，照著要求的訊號去跟DHT11溫濕度感應器溝通獲取溫濕度數據。
原理
- 使用moore狀態機來與dht11溝通
- 資料腳設為輸出，發送開始訊號
- 資料腳設為輸入，接收dht11 回傳資料
- 將資料放到signal方便其他模組讀取
- 停頓1秒左右給dht11緩衝時間
- 重複以上
- 將溫濕度integer 型態訊號轉成4位元7段顯示器顯示輸出
心得
在學習這個硬體描述語言過程中其實蠻煩躁的，因為VHDL不像普通程式語言那樣是循序執行，他是有些同步執行有些循序，所以整個邏輯思維大爆炸，完全不能套用以前寫c++、python等程式語言的想法，要邊寫邊想像合成出的電路大概長怎樣來推斷順序是什麼，就算腦袋都想好了，出來結果也可能跟想像完全不一樣😭
這次的串列通訊也花了我整整一星期的時間在debug，但當最後成功時的雀躍感真的遠遠超過使用Arduino來讀取DHT11😆
經過這次成功的經驗後，我對狀態機的使用更為熟練了，也對串列通訊有了更深的認識，debug技術也大幅提升，因為沒有邏輯分析儀，所以我用示波器來debug已經用的滾瓜爛熟了！