AN1278 datasheet(30/44 Pages) STMICROELECTRONICS

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LIN (LOCAL INTERCONNECT NETWORK) SOLUTIONS

4.2.1.3 Master data request (

DataRequest_Notification)

The application handles one data request from the master corresponding to the identifier 0x20

(

ID_Table[1]). The application has to return a pointer to an array containing the data to be

sent. In this example we declare an array “

slave_data[]”. This array will be shared between the

application updating it with the last data and the LIN communication sending its contents on

request of the master. The corresponding code for the “

DataRequest_Notification” function is:

4.2.1.4 Data reception (

DataReceived_Notification)

The application handles 2 “data” frames from the master corresponding to the identifier 0x03

and 0x80. The first frame is part of the “normal” communication. The second frame is a sleep

command frame that can be sent by the master at any time to interrupt the normal communi-

cation and set all nodes into low power mode.

On reception of the first frame the application saves the received data into the variable

“

master_data[]“.

On reception of the sleep command frame the application sets the ST7 in Halt mode. Before

setting the ST7 in Halt mode the wake-up sources should be acitivated. An application func-

tion, “PORTS_WakeUp_On()“, is called. Two pins are configured as interrupt and will wake

the ST7 up upon a corresponding interrupt request. The first pin is connected to the LIN_RX

pin (the SCI RX pin has no interrupt capability). As a result any bus activity will wake the ap-

plication up. The second is an application pin that should be also able to wake up the applica-

tion.

The corresponding code for the “

DataReceived_Notification” function is:

Any activity on the bus will wake up the ST7 out of Halt mode. As soon as the ST7 is ready to

execute the next instruction any incoming frame can be received.

The application can also be woken up by a sensor connected to one pin of the ST7 and then

should also wake up the whole LIN network. To do this, a wake-up frame has to be sent, which

is done by the “

LIN_SendWakeUpSignal()” function. This function is therefore inserted in the

application wake-up interrupt routine:

The last point to be configured is the timeout handling and the setting of the corresponding

timer, which is timer A. The application software is not using timer A for other purposes. As de-

extern uByte slave_data[];

uByte * DataRequest_Notification(@tiny t_header *header)

{

if(header->identifier == ID_Table[1].id){

return(slave_data);

}

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