Does espruino support bonding with a pin?

Hmm... If only you had an expensive imaging device somewhere that you
could use :)

Yes, all the gear, no idea ;)

Connecting in nRF and sending the wrong PIN results in the same behaviour, so there is a connection failed message on the camera which then is replaced by the no device connected screen as per the sequence when doing it from the Pixl.

This is an nRF session where I connect and put in the wrong PIN and then re-connect and put in the correct PIN

nRF Connect, 2019-02-04
Pocket Cinema Camera 4K A:1C2 (90:FD:9F:B8:CA:37)
D    18:46:51.954    gatt.close()
D    18:46:51.957    wait(200)
V    18:46:52.158    Connecting to 90:FD:9F:B8:CA:37...
D    18:46:52.158    gatt = device.connectGatt(autoConnect = false, TRANSPORT_LE)
D    18:46:52.406    [Server callback] Connection state changed with status: 0 and new state: CONNECTED (2)
I    18:46:52.406    [Server] Device with address 90:FD:9F:B8:CA:37 connected
I    18:46:52.406    [Server] MTU changed to 64
D    18:46:52.453    [Callback] Connection state changed with status: 0 and new state: CONNECTED (2)
I    18:46:52.453    Connected to 90:FD:9F:B8:CA:37
D    18:46:52.457    wait(1600ms)
D    18:46:52.484    [Broadcast] Action received: android.bluetooth.device.action.ACL_CONN­ECTED
V    18:46:54.072    Discovering services...
D    18:46:54.072    gatt.discoverServices()
D    18:46:54.087    [Callback] Services discovered with status: 0
I    18:46:54.087    Services discovered
V    18:46:54.115    Generic Access (0x1800)
- Device Name [R] (0x2A00)
- Appearance [R] (0x2A01)
Device Information (0x180A)
- Manufacturer Name String [R] (0x2A29)
- Model Number String [R] (0x2A24)
Unknown Service (291d567a-6d75-11e6-8b77-86f30ca893d3)
- Unknown Characteristic [W] (5dd3465f-1aee-4299-8493-d2eca2f8e1bb)
- Unknown Characteristic [I] (b864e140-76a0-416a-bf30-5876504537d9)
 Client Characteristic Configuration (0x2902)
- Unknown Characteristic [N] (6d8f2110-86f1-41bf-9afb-451d87e976c8)
 Client Characteristic Configuration (0x2902)
- Unknown Characteristic [N R W] (7fe8691d-95dc-4fc5-8abd-ca74339b51b9)
 Client Characteristic Configuration (0x2902)
- Unknown Characteristic [W] (ffac0c52-c9fb-41a0-b063-cc76282eb89c)
- Unknown Characteristic [R] (8f1fd018-b508-456f-8f82-3d392bee2706)
D    18:46:54.116    gatt.setCharacteristicNotification(b864e­140-76a0-416a-bf30-5876504537d9, true)
D    18:46:54.119    gatt.setCharacteristicNotification(6d8f2­110-86f1-41bf-9afb-451d87e976c8, true)
D    18:46:54.122    gatt.setCharacteristicNotification(7fe86­91d-95dc-4fc5-8abd-ca74339b51b9, true)
V    18:47:09.481    Writing request to characteristic 5dd3465f-1aee-4299-8493-d2eca2f8e1bb
D    18:47:09.481    gatt.writeCharacteristic(5dd3465f-1aee-4­299-8493-d2eca2f8e1bb, value=0xFF04000000010000)
D    18:47:09.904    [Broadcast] Action received: android.bluetooth.device.action.BOND_STA­TE_CHANGED, bond state changed to: BOND_BONDING (11)
D    18:47:09.920    [Broadcast] Action received: android.bluetooth.device.action.PAIRING_­REQUEST, pairing variant: PAIRING_VARIANT_PIN (0)
D    18:47:18.238    [Broadcast] Action received: android.bluetooth.device.action.BOND_STA­TE_CHANGED, bond state changed to: BOND_NONE (10)
I    18:47:18.238    Bonding failed
D    18:47:21.182    [Server callback] Connection state changed with status: 0 and new state: DISCONNECTED (0)
I    18:47:21.182    [Server] Device disconnected
D    18:47:21.196    [Callback] Connection state changed with status: 22 and new state: DISCONNECTED (0)
E    18:47:21.197    Error 22 (0x16): GATT CONN TERMINATE LOCAL HOST
I    18:47:21.197    Disconnected
D    18:47:21.290    [Broadcast] Action received: android.bluetooth.device.action.ACL_DISC­ONNECTED
D    18:47:48.789    gatt.close()
D    18:47:48.791    wait(200)
V    18:47:48.992    Connecting to 90:FD:9F:B8:CA:37...
D    18:47:48.992    gatt = device.connectGatt(autoConnect = false, TRANSPORT_LE)
D    18:47:49.292    [Server callback] Connection state changed with status: 0 and new state: CONNECTED (2)
I    18:47:49.292    [Server] Device with address 90:FD:9F:B8:CA:37 connected
I    18:47:49.292    [Server] MTU changed to 64
D    18:47:49.400    [Callback] Connection state changed with status: 0 and new state: CONNECTED (2)
D    18:47:49.400    [Broadcast] Action received: android.bluetooth.device.action.ACL_CONN­ECTED
I    18:47:49.400    Connected to 90:FD:9F:B8:CA:37
V    18:47:49.422    Discovering services...
D    18:47:49.422    gatt.discoverServices()
D    18:47:50.038    [Callback] Services discovered with status: 0
I    18:47:50.039    Services discovered
V    18:47:50.062    Generic Access (0x1800)
- Device Name [R] (0x2A00)
- Appearance [R] (0x2A01)
Device Information (0x180A)
- Manufacturer Name String [R] (0x2A29)
- Model Number String [R] (0x2A24)
Unknown Service (291d567a-6d75-11e6-8b77-86f30ca893d3)
- Unknown Characteristic [W] (5dd3465f-1aee-4299-8493-d2eca2f8e1bb)
- Unknown Characteristic [I] (b864e140-76a0-416a-bf30-5876504537d9)
 Client Characteristic Configuration (0x2902)
- Unknown Characteristic [N] (6d8f2110-86f1-41bf-9afb-451d87e976c8)
 Client Characteristic Configuration (0x2902)
- Unknown Characteristic [N R W] (7fe8691d-95dc-4fc5-8abd-ca74339b51b9)
 Client Characteristic Configuration (0x2902)
- Unknown Characteristic [W] (ffac0c52-c9fb-41a0-b063-cc76282eb89c)
- Unknown Characteristic [R] (8f1fd018-b508-456f-8f82-3d392bee2706)
D    18:47:50.062    gatt.setCharacteristicNotification(b864e­140-76a0-416a-bf30-5876504537d9, true)
D    18:47:50.065    gatt.setCharacteristicNotification(6d8f2­110-86f1-41bf-9afb-451d87e976c8, true)
D    18:47:50.068    gatt.setCharacteristicNotification(7fe86­91d-95dc-4fc5-8abd-ca74339b51b9, true)
V    18:48:01.291    Writing request to characteristic 5dd3465f-1aee-4299-8493-d2eca2f8e1bb
D    18:48:01.291    gatt.writeCharacteristic(5dd3465f-1aee-4­299-8493-d2eca2f8e1bb, value=0xFF04000000010000)
D    18:48:01.778    [Broadcast] Action received: android.bluetooth.device.action.BOND_STA­TE_CHANGED, bond state changed to: BOND_BONDING (11)
D    18:48:01.778    [Broadcast] Action received: android.bluetooth.device.action.PAIRING_­REQUEST, pairing variant: PAIRING_VARIANT_PIN (0)
D    18:48:12.993    [Broadcast] Action received: android.bluetooth.device.action.BOND_STA­TE_CHANGED, bond state changed to: BOND_BONDED (12)
I    18:48:12.994    Device bonded
I    18:48:13.021    Data written to 5dd3465f-1aee-4299-8493-d2eca2f8e1bb, value: (0x) FF-04-00-00-00-01-00-00
A    18:48:13.021    "(0x) FF-04-00-00-00-01-00-00" sent
V    18:48:19.171    [Server] Cancelling server connection...
D    18:48:19.171    server.cancelConnection(device)
V    18:48:19.179    Disconnecting...
D    18:48:19.179    gatt.disconnect()
D    18:48:19.191    [Callback] Connection state changed with status: 0 and new state: DISCONNECTED (0)
I    18:48:19.191    Disconnected
D    18:48:20.229    [Server callback] Connection state changed with status: 0 and new state: DISCONNECTED (0)
I    18:48:20.229    [Server] Device disconnected
D    18:48:20.259    [Broadcast] Action received: android.bluetooth.device.action.ACL_DISC­ONNECTED

Changing the NRF.setSecurity doesn't change the behaviour and the PIN prompt will only be invoked on the camera and the passkeyRequest triggered if startBonding is included.

I changed the Write function so that it retains the startBonding but doesn't disconnect after writing to the characteristic. This leaves the PIN prompt up on the camera in the waiting state so gives me a chance to then pass the PIN to it but again it invokes the connection failure on the camera.

With the behaviour being identical by passing the wrong PIN when connected through nRF it does appear to point to the the problem being the PIN being mangled on its way from the Pixl.