topic Re: UART TXEN will not enable in LPC Microcontrollers

UART TXEN will not enable

lpcware — Wed, 15 Jun 2016 16:38:21 GMT

Content originally posted in LPCWare by bunrockter on Sat Aug 25 22:42:29 MST 2012
I am using the LPC4350 on a Hitex eval boar,d and I am having trouble getting UART1 up and running. I am only using the RX & TX lines, I am not using any of the modem or handshaking lines. I have followed the code examples provided by the Hitex website, but I am still seeing the same issue:

When I try to enable the transmitter by writing a 1 to bit 7 of the TEN register it remains 0;

LPC_UART1->TER = 0x80UL; //Enable transmit
temp = LPC_UART1->TER;

temp always reads zero.

I don't seem to get anything out when I hook up terra term either, although I have seen the RBR register change when I have sent info from terra term.

The user manual said that this bit should default to on (1) after reset, but the debugger always reads a zero as well.

Is this a write only register? does anyone else see the TXEN bit go high when they write to it?

Re: UART TXEN will not enable

lpcware — Wed, 15 Jun 2016 16:38:22 GMT

Content originally posted in LPCWare by Karl on Sun Aug 26 22:29:02 MST 2012
The User Manual is wrong here.

Just like UART0/2/3 of the LPC4350, the TXEN bit of the TER register is no longer in bit position 7, but rather in bit position 0!
Also the address offset of the TER register is 0x5C, not 0x30.

Re: UART TXEN will not enable

lpcware — Wed, 15 Jun 2016 16:38:22 GMT

Content originally posted in LPCWare by bunrockter on Mon Aug 27 15:24:26 MST 2012
Thanks for the reply, I am able to read and write a 1 to that address, but now I am getting framing errors upon receiving, and I still can't transmit. Is there anything else in the User Manual with regards to UART1 that is incorrect? I looked for errata for the User Manual, but I only found the silicon errata. Any info would be greatly appreciated.

I am using the PLL1 clock at 120 MHz as the source for UART1 and loading 1 into DML & 237 into DLL (the devisors). With the formula in the user manual of bitRate = inputClock/(16*(256*DML + DLL)) that gives me 115213 which should be within error tolerances.

Maybe I will have to invest in a logic analyzer.

Thanks,

Bun

Re: UART TXEN will not enable

lpcware — Wed, 15 Jun 2016 16:38:23 GMT

Content originally posted in LPCWare by jdurand on Tue Aug 28 07:50:07 MST 2012
This guy
http://www.saleae.com/
makes very nice, low cost analyzers. I use one all the time, well worth the money.

There's some clones out there of his early version, but I'd still buy the real one from him.

Re: UART TXEN will not enable

lpcware — Wed, 15 Jun 2016 16:38:24 GMT

Content originally posted in LPCWare by bunrockter on Tue Aug 28 15:40:20 MST 2012
I've got a logicport coming. I am not happy with its buffer size, but it has 34 channels and runs at 500 MHZ (200 MHz if clocking from an external signal).

Re: UART TXEN will not enable

lpcware — Wed, 15 Jun 2016 16:38:24 GMT

Content originally posted in LPCWare by bunrockter on Wed Aug 29 13:20:13 MST 2012
Thanks Karl. I lowered the baud rate to 9600 and I am now able to send and receive. I will have to play with the rate and see how fast I can get it to go.

Bun

Re: UART TXEN will not enable

lpcware — Wed, 15 Jun 2016 16:38:25 GMT

Content originally posted in LPCWare by jdurand on Wed Aug 29 18:58:05 MST 2012
I'm running the UART at 250,000 bits/second on both LPC1113 and LPC1754 parts. No problems at all.

Re: UART TXEN will not enable

lpcware — Wed, 15 Jun 2016 16:38:26 GMT

Content originally posted in LPCWare by bunrockter on Thu Sep 27 14:13:10 MST 2012
Is the baudrate calculation for UART 1 in the LPC4350 usrs manual correct? I was able to get the serial port to run at 115200, but only after putting a logic scope on the lines and manually adjusting the clock values until it measured right.