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OUT OF YOUR HANDS

A PC Interface for Hand-Held Devices
by Kock Kin Ko

Start • Creating GUI and Menu • PC Interface Software • CVI Windows Programming Basics • Working Together • Plotting Performance Graphs • How Serial Com Operates • Big Endian Data Becomes Little • Sources 

HOW SERIAL COM OPERATES

The callback function Quitcom(), shown in Listing 4, executes six functions: GetCtrlVal() to read in the comport value selected by user; OpenComConfig() to set up the COM port with parameter 2400 bps, 8N1, 512-byte queue size for input and output; DisplayRS232Error() to display any error in setting up the COM port; SetComTime() to set 5-s timeout limit on communication with hand-held unit; SetCtrlAttibute() to turn the "Com Link SetUP" LED green; and InstallComCallback() to enable comCallback() to intercept serial com events in real time.

Listing 5 shows the function codes for send_password(), which further executes the following functions: StringLength() to find out the length of the password send_data; ComWrt() to write the password to com port; SetCtrlAttribute() to turn the PassWordSent LED to green color; and ReturnRS232Err() to check if any RS-232 errors occurred.

The code for Show_count_down() is shown in Listing 6. The function displays the RxCountDown panel by InstallPopup(), initializes remain_time to 5-s, displays the remain_time value on the panel by executing SetCtrlVal(), and enables the timer to tick by SetCtrlAttribute().

While the timer is on, Count_down(), shown in Listing 6, intercepts the 0.25-s tick event and executes the following codes: remain_time is reduced by 0.25 s; SetCtrlVal() puts the updated remain_time value on the panel:, and when remain_time is down-counted to zero, quit_count_down() kills both the panel and the timer.

Listing 7 shows the code for receive_data(). It calls ComRdTerm() to read the LF-terminated data from the COM port and load the data into a buffer read_data, CopyString() to append a NULL to the read_data, SetCtrlVal() to display the NULL-terminated data on the main-panel textbox, ReturnRS232Err() to check for RS-232 errors, and SetCtrlAttribute() to turn the main-panel RxNewData LED green if no RS-232 errors are found.

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