Preliminary T470 wiring
This early plan mapped a T470 keyboard and TrackPoint to a HolyIOT 18010 module. It was not manufactured as Revision A. The T470 work now starts with the Revision B connector and the universal adapter connector.
Confirmed work
- The keyboard uses a 40-contact, 0.5 mm FFC plus a separate J37 TrackPoint and backlight connector.
- The firmware supports the complete 84-key matrix and Fn media controls.
- Backlight power and PWM are separate signals.
The current T470 firmware does not enable the TrackPoint, keyboard LEDs, or backlight. The following electrical requirements come from the connector design and earlier ThinkPad work; they still need validation on T470 hardware:
- PS/2 DATA and CLOCK require level shifting between the TrackPoint supply and the 3.0 V nRF52840.
- TrackPoint reset requires an open-drain sink or equivalent driver.
- Keyboard indicator inputs require transistor sinks if they are confirmed as active low.
Backlight measurements
The T470 keyboard backlight was tested with 50 kHz PWM:
| Duty cycle | Measured current | Result |
|---|---|---|
| 80% | 595 mA | Stable |
| 85% | 620 mA | Stable |
| 90% | Not measured | The Analog Discovery supply shut down |
The 90% result marks a limit in the test setup, not a measured keyboard current or a confirmed keyboard fault. Repeat the test with a suitable current-limited supply and record the supply voltage, voltage at the keyboard, and current-limit setting.
These results exceed the provisional 500 mA backlight budget before full duty. Revision B must either support the measured load or enforce a tested brightness limit. Include keyboard logic, TrackPoint, radio, and battery charging when checking the complete USB power budget.
The DK wiring was useful for firmware development but was not a PCB release definition. Connector orientation, pin numbering, voltage levels, current, and mechanical fit still require first-article checks on Revision B.