User manual

WiFly GSX/EZX
www.rovingnetworks.com WiFly-RN-UM 11/9/2011
809 University Avenue • Los Gatos, CA 95032 • Tel [phone] • [e-mail]
~ 39 ~
10.3. Wake on UART
When the module is in sleep mode, the UART itself is disabled. However, wake on UART can be
accomplished by connecting the SENSE pins to the RX data or CTS pin. (Using the appropriate divider
resistors mentioned above)
The RN-134 and the RN-174 development boards have a built in resistor divider connecting SENSE 0 and
SENSE 1 to RXD and CTS respectively. This allows wake on RX and CTS using a 3.3V signal.
NOTE: Do not apply 3.3V directly to SENSE 0 and SENSE 1. Under no conditions should the voltage
on any sensor input exceed 1.2VDC. Permanent damage to the module will result.
NOTE: On the SuRF board (RN-134) rev 2 the resistor pack connecting RX and CTS signals is not
correctly connected to the sensors. To wake on UART RX place a jumper from pin 3 on the Evaluation
board header to pin 2 on the sensor header. To wake on UART CTS place a jumper from pin 10 on the
Evaluation board header to pin 3 on the sensor header.
To enable wake on RXD, use set sys trig 1.
It should be noted that the first (or possibly multiple) byte sent into the module will likely be lost, so the
designer should take care to send a preamble byte to wake up the module before sending valid data bytes. A
better way to do this is to use the CTS input to wake the module, and wait until it is ready to accept data.
To enable this, use set sys trig 2.
10.4. UART Receiver, RTS/CTS Hardware Flow Control
The UART receive buffer is approx. 1500 bytes, and at lower baudrates (less than 115K) the system can
send data over TCP/IP without the need for flow control.
Depending on the frequency and quantity of data begin sent, the comm parameters will optimize Wi-Fi
performance by specifying when the system sends IP packets. To minimize latency and TCP/IP overhead
use the flush size or match character to send data in a single IP packet. In most cases you will want to set
the flush timer to a large number to avoid fragmentation. For high throughput cases increase the UART
baudrate, set the flush size to 1460 and flush timer to a large value so full IP packets are sent.
You can control the packet forwarding 3 ways:
set comm match <value> sets the value of the packet terminator. Each time the match character is seen
an IP packet will be sent. "set comm match 0xd" for example forwards once a 0xd hex character is seen.
set comm size <value> sets the flush size, the size is the number of bytes received before forwarding.
Maximum value = 1460 bytes which is the size of a single Ethernet frame.