I had a look around the site and did not find an answer...

What is the maximum baud rate for serial communications?  I need to send a lot of data at a high speed over USB.  I'm going to use the built in USB or FTDI serial to USB converter chips.  I did some experimenting and it seems like the maximum baud rate that the mBed supports is 115200 (v24 of library).

Serial pc(USBTX, USBRX);
pc.baud(115200);

Thanks.

OK, I see an example using 921600 baud.  I tried that and it works.  However, many baud rates between 115200 and 921600 don't work.  So, I;d like to revise my question to..... What are all of the valid baud rates for Serial?

I would think they should be listed in the Serial page if the Handbook... http://mbed.org/handbook/Serial or http://mbed.org/projects/libraries/api/mbed/trunk/Serial#Serial.baud ??

Hmmm, I did an update to the libraries in May (http://mbed.org/blog/entry/135/) which is supposed to support the non-standard baud rates. Could you tell me which baud rates you have tried, which are not working? I know it handled the 1,000,000 baud rate the stepper motors used in the Etch-a-Sketch demo.

Just realised that you were talking about the host/mbed serial link - sorry, I blame a lack of coffee.

I will talk to our resident expert, and try and get a definitive list of supported baud rates. I believe that 921600 is the fastest it will go, however, and some people have had difficulties at that speed.

Freddie,

Beware of the fact that MBED does not support handshaking which makes high-speed transfers a bit shaky.  I.e. you may lose characters in both directions if the UART buffer overflows due to a lag in the receiving end.

Anders

Jon Ward wrote:

Just realised that you were talking about the host/mbed serial link - sorry, I blame a lack of coffee.

I will talk to our resident expert, and try and get a definitive list of supported baud rates. I believe that 921600 is the fastest it will go, however, and some people have had difficulties at that speed.

Jon,

Were you ever able to get a definitive list of supported baud rates?  Will it support odd baud rates like 15762 baud?  Thanks.

Sorry Freddie, I've been on holiday, and this dropped off of the stack. I will chase this up today.

The list of supported baud rates is:

110, 300, 600, 1200, 2400, 4800, 9600, 14400, 19200, 38400, 57600, 115200, 230400, 460800, 921600

I've been trying to use python to serially connect to my mbed, but i'm having problems with baud rates other than 9600. Could someone suggest a solution?

Can't we have 200 as well ? The above baud rates , as I understand , are all multiplies of 300 baud .How is 110 baud then produced (not 150 ? ).

XM: Historic starting near teletype age. 110baud is very early modems, rest came as multiples of 300baud later. I've seen 150 but not 200. No reason can't have 200, someone would just need to modify the code with that definition, but if you check things like Win8 Com Port settings you won't see 200 as it isn't a standard. While most MCU these days allow setting any baud rate, many UART chips had a register for selecting only specific baud rates.

Jivitesh: Hope you resolved this. Define problems: no connect, no data, totally garbage data, occasional errors... Some possibilities: too much frequency error on those other baud rates causing glitches (May Depend on CPU crystal divisible frequencies), does your MCU divide the clock before sending to UART module thus reducing resolution/options, what UART baud rates are supported in your hardware?

FYI: Max baud rate for UART depends on frequency error between crystals and chosen baud rates at both ends. If the MCU crystal at either end isn't an exact multiple of the selected baud rate then some baudrates will have more error than others and just fail, that's just math. Check: CrystalFrequency/baudrate give an integer that MCU can program as a divider, or is there a significant remainder? Do for both ends. If you have an oscilloscope then measure the actual baudrate transmitted by either end to compare your requested baudrate versus actual. To be compatible with other people's hardware don't push it.

looking for a part time job, thank you, albert

The Standard baud rates Comes from the sixties. The baudrates are multiply from 75 baud
75*1 = 75 baud
75*2 = 150 baud
75*4 = 300 baud
...

The 110 baud comes from the old acoustic coupler modem

But there are not common baudrates like MIDI with a baud rate of 31250.

The max baud rate of the most serial ports and usb to serial ports is 115200.
230400, 460800 and 921600 is not availlable at the most usb to serial ports.
Older serial ports goes up to 57600 baud

But for long cables the max baud rates is lower.
Then it depends on the voltage level. Valid signals detected > +3V and < -3V.
The common voltage is +15V and -15V but some serial ports are only driven by +-8V or some driven at +-5V
So you must check the cable length, cable quality and the voltage level to define the max baud rate.

Hi Gottfried, Are you able to send valid dmx? It seems as if only the 512 datachannels are transmit without break, MAB of startcode. Could this be due to the old LPC _uart typeset?

Hi, I will communicate stm32l011 & esp-wroom-02 with LPUART. For 115200 baud rate, 4.2 MHZ MSI oscillator is eneough ? Thank you