AN3269

Application description

Doc ID 17904 Rev 1

9/19

1.5.2

Bias current record

This operation consists of storing in memory the value of the bias current inherent to

operational amplifier A (see Figure 2) of your STM8L-DISCOVERY. The bias current value is

taken into account for low power measurements in order to minimize measurement errors.

Once recorded, this value does not need to be refreshed and is kept in non-volatile memory

for future use. It is recommended to perform this operation when you start your evaluation in

order to obtain the best precision.

This mode is only accessible at application power-up by executing the following actions in

the order below:

●

Switch OFF STM8L-DISCOVERY

●

●

Maintain USER push-button pressed while switching ON the STM8L-DISCOVERY

●

At power on, a scrolling message “Bias Current” is displayed

●

Release the USER push-button; the bias current value is displayed and immediately

stored in non-volatile memory

Once this operation completed, replace JP1 in ON position so that the measurement

1.5.3

Manufacturing test

You can access this mode while Demo mode is running, by pressing the USER push-button

for more than 3 seconds and by releasing it. This allows you to verify that the hardware

modules needed by the STM8L-DISCOVERY for this example are working properly.

lower and upper limits. For each test function, the application displays “OK” and the

measured values when available. If all checks are successfully completed, then the

message “TEST OK” is continuously displayed. If one of the tests fails, then the application

alerts the user by continuously displaying the test name followed by “NO OK”.

To exit this manufacturing test, press the RESET button.

Note:

Generally, if the manufacturing test is not successful, first check that JP1 is placed in the ON

position and that solder bridges SB11 to SB17 are shorted. If errors are found in the Low

performed again.

1.6

Low power modes

The low power modes used in this application example are:

●

Low power run mode (with or without LCD): In this mode the CPU and some of the

peripherals are running. As selected, the LCD can be used or not. In the latter case, the

LCD and the RTC clock are disabled to save power and GPIOs are placed in output

push-pull configuration to limit consumption. During Low power run mode, the code is

executed from RAM and CPU is clocked by the LSI oscillator. Flash and data EEPROM

are stopped and the voltage regulator is configured in Ultra low power mode. The