Serial Console¶
The serial console is UART3 at 3.3 V TTL levels. Configure the terminal at 115200 baud, 8 data bits, no parity, 1 stop bit (115200 8N1), with no flow control. Do not connect a true RS-232 adapter directly; use a 3.3 V USB-to-TTL serial adapter.
AUX connector pinout¶
Devices which have an AUX-in port reuse that same connector for serial console. The AUX connector uses an unusual 3.5 mm, five-conductor TRRS plug. From the tip towards the sleeve, its contacts are:
| Contact | Signal |
|---|---|
| Tip | AUX left audio |
| Ring 1 | AUX right audio |
| Ring 2 | Ground |
| Sleeve | Device UART RX |
| Outer ring | Device UART TX |
You can find this information also in the Service Manuals.
The likely connector is the five-conductor, outer-ring SP-35501-OM. Some plugs sold as TRRRS do not have the required outer-ring geometry and do not contact this pin. Check the mechanical drawing before buying a plug.
For temporary receive-only access, the outer ring can be contacted with probe tweezers. Connect the adapter ground as above and probe the outer ring with the adapter RX lead.
Wiring directly to the PCB¶
As an alternative to making a five-conductor plug, open the device and solder wires to the PCB's UART3 TX, UART3 RX, and ground connections. Cross TX and RX between the device and the USB-to-TTL adapter. Use suitable ESD precautions and avoid applying power through the serial adapter.
Service port¶
On devices without AUX-in, there is instead a normal 3.5mm TRS connector, usually labeled "Service", which gives access to the serial console.
| Contact | Signal |
|---|---|
| Tip | Device UART TX |
| Ring 1 | Device UART RX |
| Sleeve | Ground |