I'm having a similar problem with iOS 7 (including DP3), except that for me I have a characteristic that has the properties set for Write & Read & Notify, and I can complete the setNotifyValue and the callback, but when I attempt to write to the characteristic I get the error message that you reported. Same code works fine, with the same device, on iOS 6. Here's my error message: 2013-07-09 21:34:22.441 HOBOmobile[229:60b] <MXBLEDevice.m:(1552)> didWriteValueForCharacteristic: error report = Error Domain=CBErrorDomain Code=0 "Unknown error." UserInfo=0x16550980 {NSLocalizedDescription=Unknown error.} On 6/29/13 3:00 PM, "bluetooth-dev-request@lists.apple.com" <bluetooth-dev-request@lists.apple.com> wrote:

Date: Fri, 28 Jun 2013 16:40:27 -0500 From: Qinghui Tang <tangqinghui@hotmail.com> To: "bluetooth-dev@lists.apple.com" <bluetooth-dev@lists.apple.com> Subject: Notification could be enabled Message-ID: <BLU162-W6D4B972CB33A57EF3565DB6760@phx.gbl> Content-Type: text/plain; charset="iso-8859-1"

One of characteristics has the property Write & Read & Notify & Indicate.When I called setNotifyValue:forCharacteristic, the delegate functiondidUpdateNotificationStateForCharacteristic was invoked with error: Error Domain=CBErrorDomain Code=0 "Unknown error." UserInfo=0x1cdb6760 {NSLocalizedDescription=Unknown error.} Therefore, although my peripheral did send notification (observed with TI smart sniffer),but iOS function didUpdateValueForCharacteristic was never called. Anyone got an idea what may cause the failure of enabling notification?