I haven't used any OBD equipment yet. I just wrote a C program that send and receive a byte at 5 bps and tested it with a loopback device. The program that I'm writing will be used with an OBD device later but not yet. I need to make sure my program behave as expected first before to connect it to the OBD device. This is why I'm trying to figure out why it's taking so long to do both operations. Like I said I was expecting to be able to do both in less than 3 seconds. I'm thinking there might be something wrong with Linux or with the program that I wrote. I do agree with you that I should not expect any help in this forum about my OBD device.

thanks again!