PlayBook shipments dropped in half for Research In Motion during its second quarter, which also saw revenue continue its steep decline.

RIM shipped just 200,000 PlayBooks in the second quarter, down from 500,000 last quarter, when it started offering the tablet device.

Revenue was US$4.2 billion, hitting the low end of the company’s expectation and down 10 percent from the same quarter last year. Analysts polled by Thomson Financial expected $4.47 billion.

RIM’s net income was $329 million, or $0.63 per share. Adjusted net income was $419 million, or $0.80 per share. Analysts were expecting better: Those polled by Thomson predicted $0.87 per share.

RIM shipped 10.6 million smartphones during the second quarter. In June, RIM warned that the second quarter might be weak because of delays in shipping new phones. The delays meant RIM would miss the back-to-school sales period, negatively impacting sales, it said at the time.

Executives who spoke during a conference call to discuss the results put a positive spin on phone sales, however. The company only began launching phones running the new BlackBerry 7 software within the past few weeks, and so far it’s the “largest and most successful launch in our history,” Mike Lazaridis, co-CEO of RIM, said during the call.

BlackBerry 7 is based on the company’s existing OS, but it is designed to serve as a transition to a new operating system that RIM is developing based on technology from QNX, a company it acquired.

RIM expects the bulk of phones next year to be based on BlackBerry 7, with QNX phones representing a subset of high-end devices.