[nRF51822] TX function failed at nRF UART app of iPhone 4S (iOS7)

Question

Hi
Before, TX and RX functions run well at iOS6. After we updated to iOS7, RX still worked but TX couldn't send out data. Did you verify nRF UART app at iOS7?

Ole Morten · Accepted Answer

Have you updated to the latest version, 1.0.1? With this version, this should work without any problems. 
 You're right that there was a change in write behavior with iOS 7, but the UART app should still work, as long as you make sure to use the latest version on both the phone and the nRF51. The problem came from a difference between the nRF51 code and the iOS app; the nRF51 expected a Write Command (write without response), while the iOS app sent a Write Request (write). In iOS 6, it seems the Write Request was automatically downgraded to a Write Command, but this does not happen on iOS 7, hence the failure. This should however be fixed in the latest version of nRF UART, which does either a Write Command or a Write Request, depending on what the characteristic support. 
 This problem was also discussed here .