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NXPTM M522XX, KINETIS and i.MX RT / MCF52235 UARTS and UART Interrupts -> no transmit complete int?
« on: January 28, 2010, 01:29:32 AM »
I was going to experiment using MCF52235 UARTs with RS485 but have just discovered that the only transmit interrupt available is effectively Transmit Data Register Empty (TXRDY).
But for RS485 you need to know when it is safe to switch the transmit enable bit on the RS485 driver. That is, you need to know when the byte has completely finished transmitting, stop bit and all. It would have been nice for there to be a transmit complete (TXEMP) interrupt but this seems to be lacking in the UART module. I considered setting some routine/timer to check the TXEMP flag(after reception of TXRDY interrupt) but this solution isn't fast or elegant.
Is it just me or is the UART module in some (all?) of the MCF522xx devices a bit clunky?
ideas? at the moment i'm thinking i should look at some other micros but 128K program plus 128k flash storage is attractive in devices like the MCF52235.
John Dowdell
But for RS485 you need to know when it is safe to switch the transmit enable bit on the RS485 driver. That is, you need to know when the byte has completely finished transmitting, stop bit and all. It would have been nice for there to be a transmit complete (TXEMP) interrupt but this seems to be lacking in the UART module. I considered setting some routine/timer to check the TXEMP flag(after reception of TXRDY interrupt) but this solution isn't fast or elegant.
Is it just me or is the UART module in some (all?) of the MCF522xx devices a bit clunky?
ideas? at the moment i'm thinking i should look at some other micros but 128K program plus 128k flash storage is attractive in devices like the MCF52235.
John Dowdell