■ Figure 2. The JC port of the MX3cK is connected to
the Five-In-One and Combined Interface device
embedded interfaces in this manner. CTS is pin 1
of the JC connector.
respectively. The completed conversion of the Combined
Interface device to embedded development mode is
under the lights in Photo 5.
Shaking Down the Combined
■ Photo 6. The Digilent Cerebot MX3cK is designed to
interface to Digilent’s line of Pmods. The Five-In-One
and Combined Interface development mode devices
both use MX3cK portal JC.
Interface Device
The ATI command will force the local ETRX357 to
identify itself to the MX3cK. Every Telegesis HA AT
The embedded host of choice is the Cerebot MX3cK
rendered in Photo 6. We are primarily interested in the
MX3cK’s JC interface as it contains the UART2 signals.
Take another look at Figure 1 for the pinout of the
MX3cK’s JC interface. Even though we are working with
ZigBee HA hardware, the interfaces are simple RS-232
three-wire interfaces. The RTS and CTS pins are not
supported by firmware on the MX3cK side. So, only the
TX and RX signals are being driven in Figure 2, which is a
null-modem circuit established between the MX3cK and
the Combined Interface device.
To begin our shakedown, we will need some firmware
targeting the MX3cK:
void sendATI(void)
{
txBuf[0] = 0x0D; //preamble
txBuf[1] = 0x0A; //preamble
txBuf[2] = ‘A’; //command
txBuf[3] = ‘T’;
txBuf[4] = ‘I’;
txBuf[5] = 0x0D; //postamble
txBuf[6] = 0x0A; //postambleThe next step is to command the Combined Interface
to establish a network. Before we do that, we first need to
make sure that the ETRX357 does not attempt to revive a
previously established network. We do that with the
disassociate local command and a familiar snippet of code:
xmitPkt(0x07);
delayms(1000);
if(CharInQueue())
{
do{
biteIn = recvchar();
printf(“%c”,biteIn);
}while(CharInQueue());■ Screenshot 2.
Success! This
proves out the
hardware and
tells us we are
on the right
track with the
firmware driver,
as well.
September 2013 61
