iPod IWIP3G User Guide - Page 196

12.8 Wireless IO Replacement iWRAPs can be used to do wireless IO replacement, that is, to transmit the status of GPIO PINs over the SPP link. This means that if the status of the local IO changes, so does the status of the remote IO. This functionality can be accomplished by using the MSC (Modem Status Control) feature in iWRAP. Host iWRAP iWRAP Host SET BT AUTH * {pin} SET BT AUTH * {pin} SET CONTROL MSC DTE 80 20 0 0 0 0 CALL {bd_addr} 1101 RFCOMM CALL {link_id} CONNECT {link_id} RFCOMM {channel} SET CONTROL MSC DCE 20 80 0 0 0 0 Open Bluetooth connection Connection successful RING {link_id} {bd_addr} {channel} RFCOMM Mode switch to data mode Change PIO5 status PIO7 status changes MSC status update MSC status update PIO7 status changes Change PIO5 status Figure 16: Wireless IO replacement connection The example above was done with WT12 evaluation kits. In the evaluation kit, there is a DSR button in PIO5 and a LED in PIO7. Parameter 80 matches with PIO7 and parameter 20 with PIO5. So whenever DSR button is pressed in the local device, the LED status changes in the remote end. NOTE:  Switching the IO status very rapidly may reset iWRAP as the GPIO interrupts are handled with low priority. Therefore MSC feature is not feasible for radio GPIO sampling application.  There is also a delay when transmitting the MSC status over the Bluetooth link. Without power saving in use, this delay is roughly 20ms and if power saving is in use, the delay depends on SNIFF mode parameters. 196