AN4989 datasheet(77/99 Pages) STMICROELECTRONICS

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AN4989

Troubleshooting

Table 6 summarizes solutions to overcome some of the most frequent issues faced during

debug setting and operation.

Table 6. Troubleshooting

Problem

Solution

Connection with target lost during debug of low-power

system

Ensure debug in low-power in DBGMCU register is

enabled.

Ensure SWD pin not set in analog state.

Refer to Section 4.1: SWD/JTAG pinout and to

Section 4.3: Low-power case.

Fail to get printf via SWO

Refer to Section 7.3: Printf via SWO/SWV.

An unexpected power consumption is measured for a

low-power application.

Check that low-power debug in DBGMCU register is

OFF. Beware that this register is reset only with a POR

(power-on reset).

Refer to Section 4.3.

Fail to connect to a board with Normal/System Reset

Try ConnectUnderReset / Hardware Reset connection

mode. This resets SWD connection in case it has been

disabled by application.

Refer to Section 4.2.

Fail to connect on board using

ConnectUnderReset/Hardware using ST-LINK

Ensure NRST of ST-LINK is properly connected to MCU

NRST (e.g. check SB12 for Nucleo).

Fail to see clock signal on MCO output

Ensure that the clock configured to MCO is in the

supported range of the GPIO and that the OSPEED

setting is correct.

Refer to Section 8.2.

Impossible to evaluate a value or a variable, or

impossible to set a breakpoint at a specific line in code

Compiler optimization is probably enabled. Remove it.

Refer to Chapter 3: Compiling for debug.

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