a = "0010002" + Chr(3)
MSComm1.Output = Chr(5) + Chr(2) + a+ sumcheck(a)
'以上這句改為:MSComm1.Output = Chr(2) + a+ sumcheck(a)即可!
请问a ="0010002" + Chr(3)   0010002是啥意思

看通讯协议

看下手册就清楚了