Hi,
I'm interfacing a GPS skynav SKM53 which uses UART with MCB 1700 board( onboard LPC1768 microcontroller). I have the transmitter pin of GPS connected to P2.1 (configured as UART1 Rx). Though, i can see the data in the RBR (Receive Buffer) register but I don't see the UART_IRQ handler being invoked neither are any flags being set(like LSR,RLS or RDA)
I have tested the IRQ handler by interfacing with PC (COM Port connected using RS232 cable) and it works perfectly. I use the same function for interfacing on peripheral pins of UART, it doesn't get invoked. Is there any other configuration, I need to do so as to invoke IRQ handler when data is seen on the peripheral??? Please advise.
The ST3232C is a RS-232 driver and receiver, supporting 3-5.5V on the logic-level side.
So good when your LPC17xx is connected to a PC.
But if that GPS have logic-level signalling, then you either need two ST3232C to step down to logic levels again. Or remove your current ST3232C.
One side of a ST3232C can not be connected to logic-level devices. It outputs too high voltages and can destroy logic-level devices connected on the RS-232 side.
Thank you Westermark for the reply.
I don't think I have an option to remove ST3232C chip from the board. I can only add peripherals.
I tested the output voltage from the GPS, its 2.85 v as per the datasheet and the pin which I'm connecting on the board has a description like this
“5v Tolerant pad providing digital I/O functions with TTL levels and hysteresis. This pin is pulled up to a voltage level of 2.3V to 2.6V”
So, I believe 2.85 v shouldn't cause a problem as its 5v tolerant and shouldn't it be able to pull up with 2.85v.
Do you think I need a level shifter to bring down the voltage to fall with in the range of 2.3v to 2.6 v or I can go ahead with direct interfacing?
If the controller GPIO line can detect 2.3V or above that voltage as logic level high, then following connection should work:
Controller GPS Module TxD RxD RxD TxD Gnd Gnd