HORNER HE200WCM910 User Manual page 43

RS‐232/485 RF Modem Product Manual – MAN0782‐02
RO Command (continued)
RP (RSSI PWM Timer) Command
RR (Retries) Command
When RO is the transmission-beginning criteria: The actual time between the reception of the last
character from the UART and the beginning of RF transmission will be at least 800 µsec longer
than the actual RO time to allow for transmission setup. Additionally, it is subject to 100 - 200
µsec of additional uncertainty, which could be significant for small values of RO at high UART bit
rates.
The RO timer calculates the correct UART character time (10, 11, or 12 bits) based on the
following criteria:
• 1 start bit
• 8 data bits
• 0 or 1 parity bit (as set by ATNB)
• 1 or 2 stop bits (as set by ATSB)
RP Command is used to enable a PWM ("Pulse
Width Modulation"). The pin is calibrated to show
the difference between received signal strength
and the sensitivity level of the modem. PWM
pulses vary from zero to 95 percent. Zero percent
means the received RF signal is at or below the
published sensitivity level of the modem. The
following table shows dB levels above sensitivity and PWM values:
The total time period of the PWM output is 8.32 ms. PWM output consists of 40 steps and
therefore the minimum step size is 0.208 ms.
dBm above Sensitivity
A non-zero value defines the time that PWM output is active with the RSSI value of the last
received RF packet. After the set time when no RF packets are received, PWM output is set low (0
percent PWM) until another RF packet is received. PWM output is also set low at power-up. A
parameter value of 0xFF permanently enables PWM output and always reflects the value of the
last received RF packet.
Pin 11 of the encased OEM RF module is shared between PWM output and Config input. When the
modem is powered, the Config pin is an input. During the power-up sequence, if RP parameter is
a non-zero value, the Config pin is configured as an output and set low until the first RF packet is
received. With a non-zero RP parameter, the Config pin is an input for RP ms after power up.
<Networking & Security> RR Command is used
to set/read the number of retries that can be sent
for a given RF packet. When RR Command is
enabled (non-zero value) and when MT Command
equals zero, RF packet acknowledgements and
retries are enabled.
After transmitting a packet, the transmitting modem waits to receive an acknowledgement from a
receiving modem. If the acknowledgement is not received in the period of time specified by RN
(Delay Slots) Command, the original packet is transmitted again. The RF packet is transmitted
repeatedly until an acknowledgement is received or until the packet is sent RR times.
AT Command: ATRP
Binary Command: 0x22 (34 decimal)
Parameter Range: 0 - 0xFF
Default Parameter Value: 0x20 (32 decimal)
Number of bytes returned: 1
PWM percentage
(high period / total period)
10
20
30
AT Command: ATRR
Binary Command: 0x18 (24 decimal)
Parameter Range: 0 – 0xFF
Default Parameter Value: 0x0A (10 decimal)
Number of bytes returned: 1
[x 100 milliseconds]
47.5
62.5
77.5
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