Proposed serial hardware interface frame format

This is version 1.00. let's pull it apart!

From PC to Interface:

bit\byte B11 B10 B09 B08 B07 B06 B05 B04 B03 B02 B01 B00
7                

Hour Angle parameter

MSB

 

 

 

Hour Angle
parameter

LSB

 

 

   

Declination parameter

MSB

 

 

Declination parameter

LSB

 

6                
5             Sidereal Track  
4             HA Brake off

(N/A)

Dec Brake Off
3             Move HA
<
param
Move Dec
<
param
2             Move HA
>
param
Move Dec
>
param
1             HA Motor Fast Dec Motor
Fast
0             HA Motor
Slow
Dec
Motor
Slow

This carries a simple instruction. e.g. xx,xx,xx,xx,xx,xx,xx,45,34,56,xx,xx,xx
would instruct the dish to move the HA axis slowly while the encoder reads greater than 3456. HA Brake off., No sidereal tracking.

Note we work in 16 bit encoder units: we don't know about base 60, or base 24!

From Interface to PC:

bit\byte B11 B10 B09 B08 B07 B06 B05 B04 B03 B02 B01 B00
7           Limit switch 7 Interface OK  

Hour Angle encoder

MSB

 

 

Hour Angle
encoder

LSB

 

   

Declination encoder

MSB

 

 

Declination encoder

LSB

 

6           Limit switch 6    
5           Limit switch 5    
4           Limit switch 4 HA Brake is off Dec Brake is off
3           Limit switch 3 HA motor running Eastward Dec motor running Southward
2           Limit switch 2 HA motor running  Westward Dec motor running  Northward
1           Limit switch 1 HA motor running fast Dec motor running fast
0           Limit switch 0 HA motor running slow Dec motor running slow

This reports status back to the PC. for the above example...

xx,xx,xx,xx,xx,00,15,36,f0,xx,xx,xx ....
xx,xx,xx,xx,xx,00,15,34,f0,xx,xx,xx
xx,xx,xx,xx,xx,00,15,34,58,xx,xx,xx
xx,xx,xx,xx,xx,00,10,34,54,xx,xx,xx
xx,xx,xx,xx,xx,00,00,34,52,xx,xx,xx 

Interface OK

An "Interface OK" bit reports if the interface has a problem or is operating OK.

This could be: Illegal command, safety shut down, no frame from PC in last second...

Limit switches

0 HA extreme -
1 HA safe -
2 HA safe +
3 HA extreme +
4 Dec extreme -
5 Dec safe -
6 Dec safe +
7 Dec extreme +

Looks like we need only 7 byte frames - not 12!!