lpcware

LPC824 - RTS/OEPOL problem related to Errata sheet?

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by Wojtkingson on Thu Jul 02 08:58:01 MST 2015
Hi!

I have little problem with driving my RS485 transceiver via RTS signal.

RTS signal - PIO0_8
1) fixed functions ACMP_I2, CLKIN are disabled via SWM

2) RTS function assigned to pin
Chip_SWM_MovablePinAssign(usart->swmRTS, usart->rtsPin);


3) OESEL bit set - for RTS as RS485 tx enable signal
Chip_UART_ConfigData(usart->lpcUsartNumber, (UART_CFG_DATALEN_8 | UART_CFG_PARITY_NONE | UART_CFG_STOPLEN_1 | UART_CFG_OESEL | UART_CFG_OEPOL));


RTS signal is measured directly on MCU pin without RS485 transceiver

With OEPOL = 1 and defacto same with OEPOL = 0, RTS signal is blue
[img=1600x898]http://tinypic.com/r/2z5t0l4/8[/img]



Problem:
1) Voltage level on RTS
2) Generally strange shape of RTS signal - maybe problem which is related to ERRATAsheet with TXIDLE
3) When i change setting of OEPOL, polarity didnt change

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