UM1559

Circuit description

Doc ID 023542 Rev 1

11/13

developed software. Jumper J4, used by the example software, is connected in parallel to

PB3, so either J4 or PB3 may be used.

The board layout allows for up to 5 LEDs that user developed software can use. Only LED2

is populated on the standard configuration board and the example software uses it to display

motor on/off status.

The two outputs on pins 11 and 12 of the STM8 were designed for a dual function. If a 10uF

capacitor is installed in the position marked for LED3 and LED5, the signal on the positive

terminal of each capacitor can be used as a diagnostic analog output. The capacitor, along

with the 2.2 k

Ω series resistor, forms a low pass filter that filters the PWM output from the

STM8 to provide a simple DAC function. The example software uses these two PWM

outputs to provide useful analog diagnostic signals that can be displayed on a scope. By

default, the RPM command (before accel/decel slew limiting) and actual speed are

presented. These signals can also be observed at the test points without the capacitors as a

pure PWM signal.

Note:

The circuit ground of the PCB is “hot” with respect to the AC mains so it is necessary to

operate the board from an isolated supply, such as an isolation transformer, or use an

isolated input oscilloscope to make these observations. This warning also applies to the

connection of a PC to the swim connector. The board must be powered by an isolation

transformer or the connection to the programming dongle must be through an isolating

interface.

Connector J2 is provided to give a serial data output from the UART that may be used for

diagnostics to send data to another board. The example software does not use this function.