There is no direct bus from redhill to canon, last round me and my friend walk from the redhill mrt to canon, took us about 25 mins!!! Was told to walk towards SPRING (formal PSB building), took about 15 mins from MRT! Reach Spring turn right and walk along the road for about 10 mins, you can see the red colour canon building on the left hand side.
There is a better way, consult the showroom recept. Can take bus (147 and 196) from common wealth MRT station, take from the bus stop next to a soccer field and running track. Just about 5 to 10 mins bus ride only (I went home the opposite way ;p no have to walk back to redhill mrt station.
Btw, will canon be selling any products on the spot on sat?