Problems Using Hardware Flow control on COM3 Chipworx

NETMF & Gadgeteer
1

Hi All,

I’m having trouble getting hardware flow control to work on my Chipworx COM3. The manual says the port supports this mode so I’m wondering if I’m doing something wrong when I start it up. My pc connected in loopback works using these settings so it looks like hardware flow control is not working. I can see that when Chipworkx is connected the RTS on the receiving side never enables, whereas it does when I connect my pc instead of chipworx.

SerialPort UART = new SerialPort(“COM3”, 9600);
UART.Parity = Parity.None;
UART.StopBits = StopBits.One;
UART.DataBits = 8;

        int read_count = 0;
        byte[] tx_data;
        byte[] rx_data = new byte[10];
        tx_data = Encoding.UTF8.GetBytes("AT\r\n");
        UART.Handshake = Handshake.RequestToSend;
        UART.Open();
        UART.DataReceived += new SerialDataReceivedEventHandler(UART_DataReceived);

I’ve got v1.5 of the hardware and I’m running .net micro 4.1
Any help would be appreciated.
Thanks

2

Handshaking should be fine.
What side you see the problem at…Is that RTS on the ChipworkX side (connected to CTS on your circuit)?

3

Hi Gus,
I’m connecting to a motorola G30 Modem. In rs 232 terms it’s defined as the DCE device and expects me to connect the COM3 RTS of chipworx into it’s RTS line.
I can see that the RTS line PA12 is 3.0V on chipworkx dev board and the led on the development G30 board tells me the RTS on the G30 side is High also - and hence off as it’s an active low signal.

When I connect to the G30 using my pc with hw flow control RTS on the G30 goes low ( as expected ) and serial with hw flow control works

Data is certainly being received by the G30 Modem from Chipworkx, but the G30 is unable to reply on the serial line, when I run my program from chipworkx and then switch the modem serial cable back to the pc I see the modem spit out all the responses it’s been trying to send.

Is there something I’m missing here in my setup?
I don’t think a null modem cable is needed as my pc works fine with the same cable
Should I check some of the lines on the 232 converter?
thanks
Ronan

4

Can you try it without hardware handshaking?
These should be an AT command to disable it on the modem too.
If you have a DTR signal on the modem, this should be probably be pulled low to tell the modem that the ChipworkX is ready to be connected.
Or there is an AT command to let the modem ignores DTR signal, AT&D or AT&D0 probably?

I remember that we did not get the hardware handshaking working with ChipworkX yet. I will double check with the guys here.
I notice this in the release notes:

[quote]Known Issues

Currently, COM2 handshaking is not supported.[/quote]
It is typo, actually it COM3, since COM2 has no handshaking signals at all.

5

Hi Joe,
I’ve managed to change the modem to use no flow control with my first command so I’ve got the program running now. Pity COM3 doesn’t support full hw flow control as it would have performed better than software.
Thanks
Ronan

6

Hey Joe,
So did you fix this issue already? We are trying to implement hardware flow control between Panda and ChipworkX, but doesn’t work…so we wonder if the problem is in our implementation.

7

Hardware handshaking is not supported on ChipworkX as far as I know.

8

Nice…
In the User manual is specified that COM3 supports Handshake (the table on pg.36)… Maybe you should change this :slight_smile:
But is it a hardware problem or in the firmware?