simple rs232

[wmjenkinson]

Could someone post a small script showing the rs232 reading and writing?

[rsta2]

Sure.

#include <circle/serial.h>

TShutdownMode CKernel::Run (void)
{
	...
	CSerialDevice Serial;
	Serial.Initialize (115200);

	Serial.Write ("Test\n", 5);

	char Buffer[100];
	int nBytesRead = Serial.Read (Buffer, sizeof Buffer);
	if (nBytesRead > 0)
	{
		m_Screen.Write (Buffer, nBytesRead);
	}
	...
}

[rsta2]

On which Raspberry Pi model did you test this?

[wmjenkinson]

RPI5. Pins 8 and 10 are shorted.

[rsta2]

On the RPi 5 the class CSerialDevice by default works with the UART, which is connected to the dedicated UART socket on the board. To use the UART at GPIO14/15 (pins 8/10) you can do two things:

1. Add the line DEFINE += -DSERIAL_DEVICE_DEFAULT=0 to your Config.mk file.

2. Change the instantiation of the class CSerialDevice (see code snipped above) to the following:

CSerialDevice Serial (nullptr, FALSE, 0);  // last parameter is the serial device number

This shows the mapping of the several UARTs of the RPi 5 to serial device numbers in Circle.

[wmjenkinson]

I only have the Rules.mk and config.txt files? I can't find the Config.mk file?

[wmjenkinson]

Got it working. Thanks for the help.

[wmjenkinson]

I'm receiving data from a GPS module. Say 300-400 bytes a second. I should be able to delay the receiver for 3 - 4 times a second. However this does not work. The Serial has a 4096 data buffer. However it fails to properly read the telegrams unless the delay is 50 times a second. Why?

` while (true)
{
int nResult = m_Serial->Read (Buffer, sizeof Buffer);
buffer_index = 0;

	while (nResult-- > 0)
	{
		uint8_t nema_character = Buffer[buffer_index++];

		// Process NMEA Packet Position using start character $ and end character *
		switch (nema_character){

			// telegram start
			case '$':	working_buffer->flush_buffer();
						packet_marker = true;
			break;

			// telegram terminate, invoke deferral
			case '\n':	if(packet_marker == true){

							gps_mailbox->Postmail((CTask *)to_anyone, working_page);

							//add_page(working_page);
							working_page = remove_page();
							working_buffer = working_page->buffer;

							packet_marker = false;
						}
			break;

			// buffer telegram data
			default:	working_buffer->post_to_buffer(nema_character);
			break;
		}
	}
	CScheduler::Get()->usSleep(1000000 / 100);
}`

[rsta2]

You are using the polling version of the serial driver, which has only the 16 byte device FIFO for buffering received characters. To switch to the interrupt driver please use the following constructor:

CSerialDevice Serial (CInterruptSystem::Get (), FALSE, 0);

It uses a 2048 byte buffer then, which is filled from the interrupt routine, when characters arrive.

[wmjenkinson]

Perfect, Thank you for your help.