http://www.8051projects.net/ Learn to make simple microcontroller projects, pic, 8051, avr and arm projects. download 8051 projects, tutorials, libraries, sample codes. join the microcontroller discussion forum and ask doubts regarding electronics. the best source for 8051 over internet. en-gb 2009-01-08T11:19:12-08:00 contact@nospam.com hourly 1 2000-01-01T12:00+00:00 http://www.8051projects.net/forum-t13430.html 2009-01-08T11:19:12-08:00 I am using this Atmel application note:http://www.atmel.com/dyn/resources/prod_documents/doc3ab877f2ec329.pdfI would like to work to 9600 bauds, I change the TH1 register value to 0FDH and the SR_SPEED to 4, but this application don´t works with this values.Somebody can help me?Thanks.Now works fine, we should not change the value of the TH1 register, always 0E8H.But, what are the values for SR_SPEED variable, if we have TH1=0FDH ? http://www.8051projects.net/forum-t13430.html 2009-01-08T11:19:12-08:00 Ajay I think atmel has not given much information in their application note.But what i felt from application note i explained. code is bit confusing, but still ok if it works.If you want you can try code in tutorial too. http://www.8051projects.net/forum-t13430.html 2009-01-08T11:19:12-08:00 Ajay the timer mentioned there is not the same timer you are looking for. As you can see its a software UART, so there should be someone to provide delay for minimum unit(a bit) to be transferred. This delay is kept multiple of what is loaded into timer (0xE8). and delay is maintained using a counter (si_count).so you should not play with the timer instead you just have to vary si_count variable's value to change your final baud rate.if you looked in our tutorial section, you will find software uart code in Serial Communication tutorial, which can be used with assembly as well as C programs. I am sure it will be useful for you. Drawback is you can only have half duplex communication. http://www.8051projects.net/forum-t13430.html 2009-01-08T11:19:12-08:00 Ajay [topic moved to 8051 discussion forum] http://www.8051projects.net/forum-t13430.html 2009-01-08T11:19:12-08:00 Nicolas30 Thank you Ajay, but I need to have two 9600 bauds serial port, for this reason I need to load the register TH1 with 0FDH value, in this situation I dont know which is the si_count variable to make the second serial port works properly to 9600 bauds.Many thanks http://www.8051projects.net/forum-t13430.html 2009-01-08T11:19:12-08:00 ExperimenterUK Nicolas30 wrote ...Thank you Ajay, but I need to have two 9600 bauds serial port, for this reason I need to load the register TH1 with 0FDH value, in this situation I dont know which is the si_count variable to make the second serial port works properly to 9600 bauds.Many thanks@Nicolas30As I understand the method,for hardware and software ports to be the same set si_count to 32as they do in the pdf.Just don't ask me why http://www.8051projects.net/forum-t13430.html 2009-01-08T11:19:12-08:00 Ajay well it also depends on how much speed you are using, i usually use 1200 after all its software.. http://www.8051projects.net/forum-t13430.html 2009-01-08T11:19:12-08:00 Nicolas30 I tested the web tutorial code and works fine,in the transmission there is no problem but the problem is in the reception to synchronize the data input, we can do that by pooling or through an external interrupt.Thx http://www.8051projects.net/forum-t13430.html 2009-01-08T11:19:12-08:00 Nicolas30 9600 bauds, Ok rxd ----------- int0 |____P0.5thnx. http://www.8051projects.net/forum-t13430.html 2009-01-08T11:19:12-08:00 Ajay Great Nickolas I think its the best method to use soft UART.If possible provide your proposed schematic, I will add it in my tutorial will be helpful to everyone.