B&B Electronics Zlinx ZP Series - Manual (Page 59)

Manual Documentation Number: ZP24D-250RM-SR-2508 55
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104 – www.bb-elec.com
B&B Electronics – Westlink Commercial Park – Oranmore, Galway, Ireland – Ph +353 91-792444 – Fax +353 91-792445 – www.bb-europe.com
CSMA-CA stands for "Carrier Sense Multiple Access - Collision Avoidance". Unlike
CSMA-CD (reacts to network transmissions after collisions have been detected),
CSMA-CA acts to prevent data collisions before they occur. As soon as a module
receives a packet that is to be transmitted, it checks if the channel is clear (no other
module is transmitting). If the channel is clear, the packet is sent over-the-air. If the
channel is not clear, the module waits for a randomly selected period of time, then
checks again to see if the channel is clear. After a time, the process ends and the
data is lost.
RO (Packetization Timeout)
Command
<Serial Interfacing> RO command
is used to set and read the number
of character times of intercharacter
delay required before
transmission.
RF transmission commences when data is detected in the DI (data in from host)
buffer and RO character times of silence are detected on the UART receive lines
(after receiving at least 1 byte).
RF transmission will also commence after 100 Bytes (maximum packet size) are
received in the DI buffer.
Set the RO parameter to '0' to transmit characters as they arrive instead of buffering
them into one RF packet.
RP (RSSI PWM Timer)
Command
<I/O Settings {I/O Line Passing}>
The RP command is used to
enable PWM (Pulse Width
Modulation) output on the RF
module. The output is calibrated to show the level a received RF signal is above the
sensitivity level of the module. The PWM pulses vary from 24 to 100%. Zero percent
means PWM output is inactive. One to 24% percent means the received RF signal is
at or below the published sensitivity level of the module. The following table shows
levels above sensitivity and PWM values.
The total period of the PWM output is 64 µs. Because there are 445 steps in the PWM
output, the minimum step size is 144 ns.
PWM Percentages
dB above Sensitivity
PWM percentage (high period
/ total period)
10 41%
20 58%
30 75%
A non-zero value defines the time that the PWM output will be active with the RSSI
value of the last received RF packet. After the set time when no RF packets are
received, the PWM output will be set low (0 percent PWM) until another RF packet is
AT Command: ATRO
Parameter Range:0 - 0xFF [x character times]
Default Parameter Value: 3
AT Command: ATRP
Parameter Range: 0 - 0xFF
[x 100 msec]
Default Parameter Value: 0x28 (40 decimal)