LIRC RC5 Hex Codes

[vickyg2003]

I've been trying to explain RC-5 to jyll, and I'm having trouble interpreting the IRP.



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~F:1:6

I always have a lot of trouble interpretting the multiple colons ::: in IRP, so I took a picture of the signal to see what was what.

I thought that ~F:1:6 meant the complement of bit 1 of the function expressed in 6 bits,
but that doesn't agree with what is being sent. So then I thought that meant the complement of bit 6 of the function expressed in 1 bit, but that doesn't seem to be correct either since that bit is 1 and bit 6 of the function is 1 so that's not a complement.



Can someone explain colons in IRP to me once again, so that I can correct my explanation in the protocol primer.

[cauer29]

I've been trying to explain RC-5 to jyll, and I'm having trouble interpreting the IRP.



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~F:1:6

I always have a lot of trouble interpretting the multiple colons ::: in IRP, so I took a picture of the signal to see what was what.

I thought that ~F:1:6 meant the complement of bit 1 of the function expressed in 6 bits,
but that doesn't agree with what is being sent. So then I thought that meant the complement of bit 6 of the function expressed in 1 bit, but that doesn't seem to be correct either since that bit is 1 and bit 6 of the function is 1 so that's not a complement.



Can someone explain colons in IRP to me once again, so that I can correct my explanation in the protocol primer.

As far as I can tell, ~F:1:6 means that this field is 1 bit long and it's the complement of bit 6 of the function code. Remember though, that bit 6 is the 7th bit, since we start counting at 0. So for OBCs less than 64 this bit will always be a "1" and for OBCs 64 or greater this bit will always be a "0".

A.A.

[jyll]

From Wikipedia's RC-5 protocol page:

A field bit, which denotes whether the command sent is in the lower field (logic 1 = 0 to 63 decimal) or the upper field (logic 0 = 64 to 127 decimal). The field bit was added later by Philips when it was realized that 64 commands per device were insufficient. Previously, the field bit was combined with the start bit. Many devices still use this original system.

From SB-Projects' RC-5 protocol page:

Extended RC-5 uses only one start bit. Bit S2 is transformed to command bit 6, providing for a total of 7 command bits. The value of S2 must be inverted to get the 7th command bit though!

RC-5: Start 1 / Start 2 / Toggle / Device / OBC

RC-5x: Start / Field / Toggle / Device / OBC

110 00000 000001 (RC-5)

..6..............543210
110 00000 000001 (RC-5x Lower Field OBC 0-63)

..6..............543210
100 00000 000001 (RC-5x Upper Field OBC 64-127)

[vickyg2003]

Remember though, that bit 6 is the 7th bit, since we start counting at 0. So for OBCs less than 64 this bit will always be a "1" and for OBCs 64 or greater this bit will always be a "0".

Ah, starting at zero. and >64. I should have looked at remotemaster.

[johnsfine]

~F:1:6

I always have a lot of trouble interpretting the multiple colons ::: in IRP

I think you already understand. But just in case it is still confusing, I'l give you my point of view:

~F (as you already knew) is F with every 0 bit changed to 1 and every 1 bit changed to 0.

The value after the first : is the length of the field. That is true regardless of whether there is a second :. So this field is 1 bit long.

The value after the second : is the number of bits skipped to reach the field. This is always relative to the LSB end of the value, even in MSB signals.

So working from the LSB end, of ~F, we skip 6 bits and then select the next 1 bits.

The F:6 that is later in the same IRP, using those same interpretation rules means starting from the LSB end of F, we skip 0 bits and select the next 6 bits. Notice that those bits are selected relative to the LSB end of F regardless of whether this is an MSB or LSB signal. But after selecting them, we transmit them in MSB sequence because this is an MSB signal.