Honeywell ISA100 Gen X User Manual page 56

The function ir_do_ events() is called in the round robin scheduler for processing the IR events
based on the IR event flag. Besides the 1 second and 10 second time-outs, three interrupts are used
for IR transmission and reception.
Capture event for edge detection – start of a byte reception
1.
2. Bit time-out interrupt for bit detection or transmission.
3. Inter-byte time-out for packet detection
IR reception
The function IR bit timer is called on bit timer expiry and is used for assembling the bits to
form a byte for reception or transmission. The Start bit is detected by a capture event (since it is
zero always) and from then the bits are assembled till Stop bit. Timer expiry is used for
identifying the end of bit period, and capture interrupt flag is used for identifying if the received
bit is a "0" or "1". Once the whole byte is assembled, the timer is set for 3.5 character time
expiry, that is, the next byte is expected to arrive within 3.5 character times. Once the
synchronization byte (0xC0) is received, the further bytes are considered as valid. The received
data bytes are stored in a buffer. On expiry of 3.5 character timer, the flag IR event done is set,
which indicates either a fully received packet or reception time-out. When the IR packet is fully
received, it is sent for further processing based on the source from which it is received and the
destination that the packet is directed to.
IR transmission
IR transmission is through compare mode. Outmode 5 (Reset) is used for transmitting a "0" and
Outmode 7 Set /Reset mode is used for transmitting a "1".When the entire packet is transmitted,
the IR is put back to the receive mode. Bit time expiry interrupt is also used for transmission.
LCD Display
LCD module in the Sensor board displays the following information in cyclic mode once every
2 seconds when the device has joined the network:
1. Firmware Version (TEST FIRM)
2. Join Status (DISCOVER, SECURING, JOINING, JOINED, NOT JOINED)
3. RSSI value received from the Radio (for example,.RSSI -78)
4. RSQI value received from the Radio. (for example, RSQI 243)
Prior to the device joining the network, only the firmware version and the join status is
displayed. The function "display_task()" is called every 1 second from the main loop.
56
ISA100 Gen X Radio Module User's Guide
Honeywell
Release Independent
April 2018