Wavetronix Click 500 (programmable controller) (CLK-500) - Developer Guide - Manual (Page 85)

84 CHAPTER 8 • SERIAL MESSAGE SUPPORT
The maximum value that a variable can represent is 4,294,967,296 as the value transferred
is stored in a 4-byte field. Of course to send this high of a decimal number you would need
10 digits of ASCII characters.
Note
If you need to receive a signed integer, try receiving it as an unsigned long and then
copying it into the desired data type using a type cast.
The advantage of sending data as ASCII is that it is human readable or writable in serial
terminal programs that do not have a way to intelligently display binary data. However,
many serial terminal programs display binary data in hexadecimal byte format. If you elect
to transfer data as binary information, your data messages can be much shorter. To transfer
data as binary, use a variable array (%B) to receive the bytes into the correct data type. Pay
attention to byte order when mapping bytes between an array of bytes and a desired data
type.
Directly Accessing Receive Message Variable Data
ClickMsgReadVar and ClickMsgWriteVar provide a simple way to access variable data
within a receive message. However, in some cases it may be advantageous to have direct
access to the buffer of receive data. The function ClickMsgGetRxSnapshot gives you access
to all the bytes of the last received message on each virtual port. This function allows you
to create a snapshot of the last received message. This snapshot will not be overwritten if
another message is received on the port while you are still processing the snapshot.
ClickMsgGetRxSnapshot has three parameters. The first parameter allows you to select
which virtual port data you want to read. The second parameter is a pointer that will be set
to the start of a snapshot of the receive buffer for this virtual port. The third parameter al-
lows you to create a snapshot of the last message in the receive buffer (value = 1), or simply
to access a previous snapshot (value = 0). The function returns the number of bytes cur-
rently in the snapshot receive buffer.
ClickMsgReadVar(“sec1”,&u32tmp);
newTime.Second = (unsigned char)u32tmp;
ClickMsgReadVar(“ms1”,&u32tmp);
newTime.MSec = (int)u32tmp;
ClickUtilSetTime(&newTime);
BuildTimeResponseMsg();
ClickMsgTransmit(TimeResponseMsg,V1);