LPC1769 at high speed baudrates (>3Mbaud)

juancerrudo — Wed, 23 Jan 2019 17:40:25 GMT

Hi there!

I'm using an LPC1769 to send data to a PC. I'm using UART3 to send data through a FT232H. I've changed FTDI's drivers in order to alias high baudrates to lower ones, like: (https://www.ftdichip.com/Support/Documents/AppNotes/AN_120_Aliasing_VCP_Baud_Rates.pdf )

I've tried several; 6, 4, 3 and 2Mbaud, but only manage to get it woking with 2Mbaud. I can see the data sent by the MCU to the PC with out problems but when I try to send data to the MCU the packets have errors. I think the problem migth be due to inaccuracies with the MCU baudrate.

If I meassure the FT232 speed at 3Mbaud for example I get an error of +-0,05. With the LPC1769 that difference is +-1%, could that be the problem? It seems like the FT232 is able to tolerate the MCU diferent baudrate but the MCU can't.

I think there is nothing wrong with the configuration;

DLL = 0x02

DLM = 0x00

FDR = 0x41

Anyone have any idea how to use the LPC at high baudrates? The maximum is 6.25M according to the datasheet.

Thanks!

Re: LPC1769 at high speed baudrates (>3Mbaud)

juancerrudo — Thu, 24 Jan 2019 15:48:08 GMT

I found the answer here lpc2000 | LPC17xx Mbps baud rate limitations? .

The problem seem to be the use of fractional baudrates (FDR). I had the MCU running at 120Mhz, I now have it at 96Mhz and that allows me to configure a baudrate of 6Mbit/s whit out using fractional divider.

I leave it here in case somebodu found it useful.

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LPC1769 at high speed baudrates (>3Mbaud)

Re: LPC1769 at high speed baudrates (>3Mbaud)