Monday, August 15, 2011
Redpark Serial Cable Electrical Characteristics
We decided to develop the hardware to talk over RS-232, which can be fed into an iPod using the Redpark Serial Adapter. This is a pretty neat little device; selectable speeds up to 57.6k baud (a little slow, but fine for telemetry), comes with a whole SDK to easily integrate into your app, and comes with a loopback test dongle.
Turns out, they implement it quite well!
Looking at those images, and doing some tests with my volt meter, the Redpark puts out +6V open, 30mA dead-short, and -5.6V open, -22mA dead-short. That's a lot of power! I'm going to be able to run my electronics off the RTS line no problem. The cable also appears to implement all eight data lines, which can also be rare in cheap adapters. They even meet the slew rate spec of <30V/μs, with a slew rate of only 7.5V/μs.
So long story short, Redpark didn't cut any corners here; The signals are all implemented according to spec. The iPod connector does feel a little cheapy light, and I'm a little disappointed that their demo app is just a loop-back and signalling line test, and not something at least remotely useful like a little hyperterminal app, but the BB-9 connector feels solid, and I'm certainly not longer apprehensive about building our project on this product.
Posted by Kenneth Finnegan at 8:00 PM