Auto Baudrate Generation

Hi,

   I'm developing a project using R8C/11 controller, I wanna measure baudrate of incoming message & adjust the baudrate of R8C/11 microcontroller to the baudrate of incoming message. Is it possible to measure the baudrate of incoming message(say, from PC), if so how...

Plz help me out

With Regards,

Sharan

It all depends... If the PC sends out the same character until it gets a reply it's fully possible to make an autoadjust. If it sends an "space" (0x20) it would look like: 0 00000100 1(1) (The first '0' is the startbit, the last '1' is the stopbit, could be 2 * '1' if 2 stopbit is chosen) If the baudrate on the R8C is too high the incoming value would give overflow and/or framing error, thus the baudrate om the R8C should be lowered, if the recieved data is < 0x20 the baudrate should be raised. To lower/raise You need to make a tabel of "possible" baudrates and their values in the baudrate-register.

Previously Icecap wrote:

It all depends...

If the PC sends out the same character until it gets a reply it's fully possible to make an autoadjust.

If it sends an "space" (0x20) it would look like: 0 00000100 1(1)
(The first '0' is the startbit, the last '1' is the stopbit, could be 2 * '1' if 2 stopbit is chosen)

If the baudrate on the R8C is too high the incoming value would give overflow and/or framing error, thus the baudrate om the R8C should be lowered, if the recieved data is < 0x20 the baudrate should be raised.

To lower/raise You need to make a tabel of "possible" baudrates and their values in the baudrate-register.

ok thak u,

how to detect the start bit and stop bit of the incomming message,plz helpme out

The hardware does that! (to a certain degree) All the definitions is in the datasheet, refer to that (as always). But a hint: Start recieving at the middle baudrate, see what value that comes. If a lot of framing errors comes (2 in a row) step the baudrate up one notch, reset and test again. It should also be possible to make a routine that monitors the RXD-pin and compares with the timing of a timer. If You could calculate the time for the startbit You have the baudrate. You could do this i several ways but the fewer standart baudrates used, the faster and simpler it will be.

There's an app note and code for doing auto-baud with an H8 and a separate one on the M32C on Renesas.com   Here's the link for the M32C:

http://documentation.renesas.com/eng/products/mpumcu/apn/rej05b0723_m16cap.pdf