UM1548

System overview

Doc ID 023257 Rev 1

5/14

2

System overview

2.1

Hardware design description

Figure 2.

IR transmitter in key fob enclosure

2.1.1

STEVAL-IHM037V1 IR remote transmitter

This application is based on the direct implementation of the ST application note AN2957

with slight modifications to support the three keys.

Table 1 lists the commands used for the three keys on the transmitter:

The RC5 frame is 14 bits long and comprises the following:

●

1 start bit (always 1)

●

1 field bit

●

1 toggle bit (represented in Table 1 as X). It changes state every time a key is released

and pressed again.

●

5-bit device address (32 possible addresses)

●

6-bit device instruction (64 possible instructions).

AM12361v1

Speed up

On/off

Speed down

Table 1.

RC5 commands

Key function

Device address

Device instruction

14 bits transmitted

Speed up

SAT1 [8]

Number 8 [8]

10X01000001000

On/off

SAT1 [8]

Number 0 [0]

10X01000000000

Speed down

SAT1 [8]

Balance left [27]

10X01000011011