Serial Ports - Receive Packets - Programmers Heaven

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Serial Ports - Receive Packets

samuelmoneillsamuelmoneill Posts: 14Member
Hi Guys,

I have written a program that opens Serial Com Port 1 and sends packets to an LCD Screen. That is fine. But now i need to be able to receive packets from the LCD screen. Does anyone know how I can do this?

My send_packet() code
void send_packet(COMMAND_PACKET *packet)
ubyte i;
unsigned char buffer[20];
int index;
index = 0;
buffer[index++] = packet->command;
buffer[index++] = packet->data_length;
for(i = 0 ; i < packet->data_length ; i++)
buffer[index++] = packet->data[i];

packet->CRC.as_word =
get_crc((ubyte *)&outgoing_response,outgoing_response.data_length+2,0xFFFF);
buffer[index++] = packet->CRC.as_bytes[0];
buffer[index++] = packet->CRC.as_bytes[1];

DWORD bytes_written;
bytes_written = 0;

if(TRUE != WriteFile(handle,
printf("WriteFile() failed!
[/code]outgoing_response is a packet that is defined by the manufacturers it contains command, data_length, data, CRC

This is my attempt at receiving a packet
void receive_packet(COMMAND_PACKET *packet)
ubyte i;
unsigned char readbuf[20];
unsigned char received[20];
int index;
index = 0;
DWORD bytes_read;
bytes_read = 0;
received[index++] = ReadFile(handle,
printf("ReadFile() failed!
//readbuf[index++] = packet->command;
//readbuf[index++] = packet->data_length;
for(i = 0 ; i < packet->data_length ; i++)
readbuf[index++] = packet->data[i];

packet->CRC.as_word =
get_crc((ubyte *)&incoming_command,incoming_command.data_length+2,0xFFFF);
readbuf[index++] = packet->CRC.as_bytes[0];
readbuf[index++] = packet->CRC.as_bytes[1];

", received);

This is the information from the manufacturers data sheet for the ping command

0 (0x00): Ping Command
The LCD will return the Ping Command to the host.
type = 0x00 = 010
valid data_length is 0 to 16
data[0-(data_length-1)] can be filled with any arbitrary data

The return packet is identical to the packet sent, except the type will be 0x40 (normal response, Ping Command):
type = 0x40 | 0x00 = 0x40 = 6410
data_length = (identical to received packet)
data[0-(data_length-1)] = (identical to received packet)

I am completely lost with this so any help is greatly appreciated
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