下載時顯示如下錯誤信息：
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Arduino:1.8.19 (Windows 7), 開發板："Arduino Uno"
項目使用了 934 字節，占用了 (2%) 程序存儲空間。最大為 32256 字節。全局變量使用了9字節，(0%)的動態內存，余留2039字節局部變量。最大為2048字節。
avrdude: stk500_recv(): programmer is not respondingavrdude:
stk500_getsync() attempt 1 of 10: not in sync: resp=0xd1avrdude:
stk500_recv(): programmer is not respondingavrdude:
stk500_getsync() attempt 2 of 10: not in sync: resp=0xd1avrdude:
stk500_recv(): programmer is not respondingavrdude:
stk500_getsync() attempt 3 of 10: not in sync: resp=0xd1avrdude:
stk500_recv(): programmer is not respondingavrdude:
stk500_getsync() attempt 4 of 10: not in sync: resp=0xd1avrdude:
stk500_recv(): programmer is not respondingavrdude:
stk500_getsync() attempt 5 of 10: not in sync: resp=0xd1avrdude:
stk500_recv(): programmer is not respondingavrdude:
stk500_getsync() attempt 6 of 10: not in sync: resp=0xd1avrdude:
stk500_recv(): programmer is not respondingavrdude:
stk500_getsync() attempt 7 of 10: not in sync: resp=0xd1avrdude:
stk500_recv(): programmer is not respondingavrdude:
stk500_getsync() attempt 8 of 10: not in sync: resp=0xd1avrdude:
stk500_recv(): programmer is not respondingavrdude:
stk500_getsync() attempt 9 of 10: not in sync: resp=0xd1avrdude:
stk500_recv(): programmer is not respondingavrdude:
stk500_getsync() attempt 10 of 10: not in sync: resp=0xd1Problem
uploading to board. See hc/en-us/sections/360003198300 for suggestions.
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意思是：“程序員沒有回應avrdude:”
也試過左邊CH340C部分，給STC單片機下載程序是沒有問題的，無非是在下載程序時要“冷啟動”一下STC的單片機。
在給Arduino最小系統下載程序時，也按過復位開關，也不行。
分析了Arduino UNO開發板的電路，它也是用CH340C的下載電路，本來CH340C可以不用外接晶振的，但它接了。
我也在自制的CH340C電路中加上了晶振部分，但還是不行。
請懂的朋友幫幫我，謝謝了。
