NOTE: If you experience the issues described on this page, you can enable the configuration option below to resolve it.
CONFIG_STM32_DISABLE_IDLE_SLEEP_DURING_DEBUG=y
On some architectures (like ARM Cortex-M3) Idle thread causes the core to stop using WFI (Wait For Interrupt) assembly instruction. This effectively stops clocking of the core, which is resumed only by some enabled interrupt. This causes hardware debuggers to believe that they were disconnected from the target, as they lose connection with the now stopped core. For example OpenOCD shows errors like these the moment you start the target:
Error: jtag status contains invalid mode value - communication failure
Polling target failed, GDB will be halted. Polling again in 100ms
Error: jtag status contains invalid mode value - communication failure
Polling target failed, GDB will be halted. Polling again in 300ms
Error: jtag status contains invalid mode value - communication failure
Polling target failed, GDB will be halted. Polling again in 700ms
Error: jtag status contains invalid mode value - communication failure
Polling target failed, GDB will be halted. Polling again in 1500ms
Error: jtag status contains invalid mode value - communication failure
Polling target failed, GDB will be halted. Polling again in 3100ms
Error: jtag status contains invalid mode value - communication failure
Polling target failed, GDB will be halted. Polling again in 6300ms
Error: jtag status contains invalid mode value - communication failure
Polling target failed, GDB will be halted. Polling again in 6300ms
This makes debugging the code impossible and flashing the chip is much harder - you have to connect to the chip at the right moment (when it's not disabled due to WFI) - the chances of doing that are inverse proportional to the load of your system (if your chip spends 99% of time in Idle mode, you have 1% chance of connecting and halting it).
Some ARM cores that support disabling of clocking after WFI instruction have special configuration options to make debugging possible. One example is STM32 family - with it's DBGMCU→CR register it's possible to keep the core clocked during power-down modes. If your chip supports such configuration you should put it in some early stage of initialization, like in stm32_boardinitialize() function. The following code demonstrates the change for STM32:
uint32_t cr = getreg32(STM32_DBGMCU_CR);
cr |= DBGMCU_CR_STANDBY | DBGMCU_CR_STOP | DBGMCU_CR_SLEEP;
putreg32(cr, STM32_DBGMCU_CR);
If your chip doesn't provide such options there is no other way than not using WFI instruction in up_idle() function.
It should be noted that such modification should be done only for development stage, as keeping the core clocked during power-down modes contradicts the major purpose of using them - reducing power usage.
In rare cases that you still have problems with connecting to the target (especially after power cycle), you should try connecting and halting the chip under reset (this is supported by new versions of OpenOCD), by holding the reset button while starting OpenOCD or by configuring OpenOCD to do that for you.
If you keep the RESET button pressed and run OpenOCD command to connected to it, then it will connect sucessful. After connecting you need to keep the reset button pressed until you open the telnet connection (telnet 127.0.0.1 4444) and execute “reset halt”:
& reset halt
timed out while waiting for target halted
TARGET: stm32f1x.cpu - Not halted
in procedure 'reset'
target state: halted
target halted due to debug-request, current mode: Thread
xPSR: 0x pc: 0x msp: 0x
Then release the RESET boot and it will reset correctly.
This work-around was tested on viewtool-stm32f107 board and bypassed the above error reported by OpenOCD. The SWD programmer was a STLink-V2 and this was the command to connect:
# openocd -f interface/stlink-v2.cfg -f target/stm32f1x_stlink.cfg
The OpenOCD version used was: Open On-Chip Debugger 0.8.0-dev-0c
(git commit 215c41c)
Print/exportCommunication Failure怎么办？ - 单片机/MCU论坛 -
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后使用快捷导航没有帐号？
Communication Failure怎么办？
13:18:00　　
STM32F103C8T6做的板子已经用了一个多月了，用的SWD口下载程序，昨天还能正常下载程序，今天想再调试程序，下程序提示SWD/JTAG&&Communication Failure，怎么也下进去了，但是昨天的程序也能正常运行。这是怎么回事呢？求大神指点啊
09:23:32　　
给楼主提供一个解决办法，我也是看别人的，就不写了，链接是.cn/s/blog_69e8adc30102vrkm.html，看看能不能解决楼主的问题
助理工程师
09:39:22　　
PCB在线计价下单
板子大小：
板子数量：
PCB 在线计价
Jlink固件挂了& && && && && && && && && && && && && && && && && && && && && && && &&&
16:30:16　　
按住复位键下载一次，第二次下载就就可以了
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