UM0629

STM8L1/L2 motherboard

Doc ID 15312 Rev 2

11/26

2.9

Display and input devices

Display devices available are:

●

122x32 dot-matrix serial interface LCD (U2)

●

4 general purpose LED's (LD2,3,4,5)

Input devices available are:

●

4-direction joystick

●

selection key

●

general purpose button (B2)

2.10

Bi-color LED

A bi-color LED is connected to PB0 through a voltage translator which guarantees that the

bi-color LED works when the STM8L101 is powered by an adjustable voltage from 1.8 V to

3.3 V.

2.11

Economic measurement and potentiometer RV1

The economic measurement solution is demonstrated based on the internal comparator

inside the STM8L101 and potentiometer RV1.

As shown in Figure 5, the voltage divided by resister bridge R10 and R11 can be measured

by using an internal comparator of the STM8L1, with Vref connected to channel 2 of the

comparator and an RC charge circuit connected to the COM channel of the comparator.

To measure the voltage Vin from the potentiometer:

1.

Compare Vref with the voltage on C8 which is charged by a series of pulses generated

by PC4.

2.

Record pulse number PN_Vref when the voltage on C8 reaches voltage reference Vref.

3.

Another charge pulse PN_Vin can be obtained with voltage connected to CH1 also like

PN_Vref.

4.

The voltage Vin can be calculated based on both numbers PN_Vref and PN_Vin.

Table 5.

122x32 dot matrix LCD U13

Pin on U2

Description

Pin connection

1

Vss

GND

2Vcc

+3V3

3VO

-

4

CLK

PB5

5

SID

PB6

6CS

PD1

7A

+5V

8K

GND