AN2687 datasheet(20/22 Pages) STMICROELECTRONICS

20 / 22 page

LCD demo board

AN2687

20/22

Doc ID 14296 Rev 1

6.1

Board information

The LCD demo board should be supplied by a DC voltage of 3.3 V through connector W1.

There is no regulator present on the demo board to enable the user to modify VDD and see

the impact on the LCD contrast. The maximum absolute ratings for the power supply must

be respected (please refer to the product datasheet). It is also strongly recommended not to

apply a VDD voltage higher than 3.3 V for too long.

The LCD chosen for use on the demo board is driven at 3 V, which gives a better contrast for

low-voltage range MCUs like the STM8S20xxx.

The two pieces of software attached to this application note display “STM8 LCD” and the

contrast can be tuned with the ST software patented method through two push-buttons (S1

to increase the contrast and S2 to decrease it) with the first method (LCD driver directory in

the attached zip file).

Vrms is increased by applying first VSS, then VDD (during the dead times) to the segment,

while first VDD, then VSS is applied to the COM lines.

Vrms is decreased by applying VSS to the segment during the same dead times. The

voltage average is then kept. Refer to the software attached to this application note for more

details.

The demo board uses the STM8S20xxx microcontroller and can be reprogrammed and

debugged using the SWIM communication protocol through the SWIM interface. The board

is provided with the SWIM connector.

The device can be reset by pressing switch S3 on the demo board.

AN2687 Datasheet(PDF) 20 Page - STMicroelectronics