The following pinout is used in the RapidHA Lighting firmware. The Z357PA40 module pad numbers are shown in brackets:

• PB3 (Pad 5): Relay Control. Will be driven high (logic level 1) when the light should be on and low when the light should be off.
• PB4 (Pad 6): PWM signal (can be converted to 0-10V with an additional circuit)
• PA5 (Pad 9): Network Status Indicator LED. **A transistor circuit is required to ensure that this pin is held high at startup. This pin assignment will be changing. See the note on the "PA5 Protection Circuit" page.
• PA6 (Pad 16): Button for factory reset (by driving this pin low for >5 seconds)
  
  

The following pins can be used for serial communication with a Host microcontroller:

• PB1 (Pad 17): UART TX
• PB2 (Pad 15): UART RX

PA5 Protection Circuit

Pin PA5 on the EM357 has a built-in function defined by Silicon Labs; if it is held low at startup, the EM357 will enter bootload mode.  MMB is in the process of updating the pinout to use a different pin that is available on our new Z357PA40 module. Until the new firmware implementing a different pinout is released, it is necessary to add the “protection circuit” shown below. R1 and R2 must have the same resistance.

For more information about how to integrate the Z357PA40 module in your lighting product design, see the Hardware Design Resources page.