This requires the use of rectifier bridge and inverter bridge. This is an aggregation version of mcpwm_generator_set_action_on_compare_event, which allows user to set multiple actions in one call. The basic IO operation of a capture timer is to start and stop. See also Power management for more information. The mcpwm_new_capture_channel() will return a pointer to the allocated capture channel object if the allocation succeeds. Callback function that would be invoked when capture event occurred, components/driver/mcpwm/include/driver/mcpwm_types.h, [in] MCPWM timer event data, fed by driver, [in] User data, set in mcpwm_timer_register_event_callbacks(), Whether a high priority task has been waken up by this function. Pulses must be received every 25 ms or so or the servo will turn off. Like, for example, PC6 pulled to high, then after 100ms, PB3 pulled to high, get current value on PD1 and pull PC6 low if . Please note, the argument list of mcpwm_generator_set_actions_on_compare_event() must be terminated by MCPWM_GEN_COMPARE_EVENT_ACTION_END. Capture - describes how to use the MCPWM capture module to measure the pulse width of a signal. On the contrary, calling mcpwm_del_capture_channel() and mcpwm_del_capture_timer() function will free the allocated capture channel and timer object accordingly. You can set the sync phase for the capture timer by calling mcpwm_capture_timer_set_phase_on_sync(). The earlier DC motor tutorials were focused on the Arduino UNO, while this tutorial is focused on the ESP32 development board. On the contrary, calling mcpwm_del_operator()() function will free the allocated operator object. Set generator actions on multiple MCPWM compare events. Job Description: I need to implement an existing project (AVR194 application note) to work with my setup. MCPWM operator brake event callback function. V1 and V4 form one bridge. Timer Operations and Events - describes control functions and event callbacks that supported by the MCPWM timer. fault [in] MCPWM soft fault, allocated by mcpwm_new_soft_fault(), ESP_OK: Trigger MCPWM software fault event successfully, ESP_ERR_INVALID_ARG: Trigger MCPWM software fault event failed because of invalid argument, ESP_FAIL: Trigger MCPWM software fault event failed because of other error, fault [in] MCPWM GPIO fault handle, allocated by mcpwm_new_gpio_fault(). These objects are the basis of the following IO setting and control functions. Specify from which group to allocate the capture timer. Power source to drive the motor (LiPo battery) DESCRIPTION: Brushless motors have much more satisfying results as compared to brushed motors. ESP32Servo Device Control Allows ESP32 boards to control servo, tone and analogWrite motors using Arduino semantics. brushed/brushless DC motor, RC servo motor, Switch mode based digital power conversion, Power DAC, where the duty cycle is equivalent to a DAC analog value, Calculate external pulse width, and convert it into other analog value like speed, distance, Generate Space Vector PWM (SVPWM) signals for Field Oriented Control (FOC). The main advantage of sensorless BLDC motor control is lower system cost and the main disadvantage is the motor must be moving at minimum rate to produce sufficient BEMF to be sensed. Otherwise, it will return error code. Choose the board, COM port, hold down the BOOT button, click upload and keep your finger on the BOOT button pressed. A software fault object can be allocated by calling mcpwm_new_soft_fault() function, with configuration structure mcpwm_soft_fault_config_t as the parameter. The supported brake modes are listed in the mcpwm_operator_brake_mode_t. The MCPWM capture channel can inform the user when theres a valid edge detected on the signal. Otherwise, it will return error code. All supported event callbacks are listed in the mcpwm_timer_event_callbacks_t: mcpwm_timer_event_callbacks_t::on_full sets callback function for timer when it counts to peak value. The callback function prototype is declared in mcpwm_timer_event_cb_t. mcpwm_new_soft_sync_src() will return a pointer to the allocated sync source object if the allocation succeeds. The ESC drew 2.3 amps at 12v for this speed, and that seems to be a redline current for this voltage. Enough for a controller. MCPWM timer commands, specify the way to start or stop the timer. IRAM Safe - describes tips on how to make the RMT interrupt work better along with a disabled cache. ESP32MotorControl Motor control using ESP32 MCPWM A library to ESP32 control motors using MCPWM Works only with ESP32. The parameter user_data of mcpwm_operator_register_event_callbacks() function is used to save users own context, it will be passed to the callback function directly. mcpwm_gpio_sync_src_config_t::pull_up and mcpwm_gpio_sync_src_config_t::pull_down set whether to pull up and/or pull down the GPIO internally. mcpwm_timer_config_t::count_mode sets the count mode of the timer. callback function when mcpwm operator brakes in CBC, callback function when mcpwm operator brakes in OST, The duration of the first PWM pulse, in us, components/driver/mcpwm/include/driver/mcpwm_cmpr.h, oper [in] MCPWM operator, allocated by mcpwm_new_operator(), the new comparator will be allocated from this operator, config [in] MCPWM comparator configuration, ret_cmpr [out] Returned MCPWM comparator, ESP_OK: Create MCPWM comparator successfully, ESP_ERR_INVALID_ARG: Create MCPWM comparator failed because of invalid argument, ESP_ERR_NO_MEM: Create MCPWM comparator failed because out of memory, ESP_ERR_NOT_FOUND: Create MCPWM comparator failed because cant find free resource, ESP_FAIL: Create MCPWM comparator failed because of other error, cmpr [in] MCPWM comparator handle, allocated by mcpwm_new_comparator(), ESP_OK: Delete MCPWM comparator successfully, ESP_ERR_INVALID_ARG: Delete MCPWM comparator failed because of invalid argument, ESP_FAIL: Delete MCPWM comparator failed because of other error. 0 ratings 0% found this document useful (0 votes) 0 views. mcpwm_operator_event_callbacks_t::on_brake_ost sets callback function that will be called when the operator is going to take an OST action. When the time-base counter is equal to any of the threshold value, an compare event will be generated and the MCPWM generator can update its level accordingly. Once the fault signal is active, MCPWM Operator will force all the generators into a predefined state, to protect the system from damage. One generator can set multiple actions on different brake events, by calling mcpwm_generator_set_actions_on_brake_event() with variable number of action configurations. This function will transit the channel state from init to enable. sync [in] MCPWM soft sync handle, allocated by mcpwm_new_soft_sync_src(), ESP_OK: Trigger MCPWM software sync event successfully, ESP_ERR_INVALID_ARG: Trigger MCPWM software sync event failed because of invalid argument, ESP_FAIL: Trigger MCPWM software sync event failed because of other error, Timer event, upon which MCPWM timer will generate the sync signal, The input sync signal would be routed to its sync output, Extra configuration flags for timer sync source, Whether the sync signal is active on negedge, by default, the sync signals posedge is treated as active, Extra configuration flags for GPIO sync source. Set generator actions on multiple MCPWM brake events. All supported event callbacks are listed in the mcpwm_fault_event_callbacks_t: mcpwm_fault_event_callbacks_t::on_fault_enter sets callback function that will be called when a fault is detected. Specifically, when there are no more free generators in the MCPWM operator, this function will return ESP_ERR_NOT_FOUND error. A Brushless DC motor (BLDC) 3. You can also set the compare action one by one by calling mcpwm_generator_set_action_on_compare_event() without varargs. 3Phase Motor ABOUT ActivePFC Article Balancing Battery BLDC Motor Current sensor DC Motor DC-DC Converter Download ESP32 NodeMCU ESP8266 NodeMCU IC Switching Induction Heat Inverter 220VAC IPM 3Phase PCB Design PID Control Projects . MCPWM Operator: The key module that is responsible for generating the PWM waveforms. The demand for low cost Brushless DC (BLDC) motor has increased in industrial applications. mcpwm_timer_event_callbacks_t::on_stop sets callback function for timer when it is stopped. See also Power management for more information. Sensorless brushless DC motor control with Arduino circuit: Project circuit schematic is shown below. Sometime, the software also wants to trigger a fake capture event. 1. It is a highly versatile and low-cost solution for many applications, including Internet of Things (IoT) projects, home automation, and robotics. GPIO fault in group 0 can not be detected by the operator in group 1. mcpwm_gpio_fault_config_t::gpio_num sets the GPIO number used by the fault. However, if the more classical edge delay-based dead time with polarity control is required, then the dead-time submodule should be used. The ID should belong to [0, SOC_MCPWM_GROUPS - 1] range. This system controls the BLDC motor speed more efficiently and precisely as compared to other systems. mcpwm_capture_timer_config_t::clk_src sets the clock source of the capture timer. To allocate a capture timer, you can call mcpwm_new_capture_timer() function, with configuration structure mcpwm_capture_timer_config_t as the parameter. If you have some function that should be called when particular event happens, you should hook your function to the interrupt service routine by calling mcpwm_timer_register_event_callbacks(). 2. DFR0478 FireBeetle ESP32 IOT Microcontroller (V3.0) Supports Wi-Fi & Bluetooth DFR0483 FireBeetle Covers-Gravity I O Expansion Shield FireBeetle Covers-248 LED Matrix TEL0121 FireBeetle Covers-LoRa Radio 433MHz TEL0122 FireBeetle Covers-LoRa Radio 915MHz TEL0125 FireBeetle Covers LoRa Radio 868MHz DFR0489 FireBeetle ESP8266 IOT Microcontroller Sensored 3-Phase BLDC Motor Control Using MSP430: 20 Jul 2011: Design & development. I'm looking to model 6xPWM signals to control a BLDC in Matlab/Simulink. I've been able to find information where people will us an ESC like this between their rPi and the motor but these seem to always be connected to small motors like airplane motors and not the one like what I have. Apply for similar jobs. The parameter user_data of mcpwm_timer_register_event_callbacks() function is used to save users own context, it will be passed to each callback function directly. Otherwise the recovery cant succeed. The PWM signal sent to the ESC controller must have a period of 20ms, and the fill factor of this PWM signal will determine the rotation speed of the BLDC motor. Author: Kevin Harrington,John K. Bennett Maintainer: Kevin Harrington Read the documentation Go to repository command [in] Supported command list for MCPWM timer, ESP_OK: Start or stop MCPWM timer successfully, ESP_ERR_INVALID_ARG: Start or stop MCPWM timer failed because of invalid argument, ESP_ERR_INVALID_STATE: Start or stop MCPWM timer failed because timer is not enabled, ESP_FAIL: Start or stop MCPWM timer failed because of other error, The first call to this function needs to be before the call to mcpwm_timer_enable. mcpwm_timer_config_t::update_period_on_sync sets whether to update the period value when the timer takes a sync signal. project Closed Your email address. mcpwm_generator_config_t::invert_pwm sets whether to invert the PWM signal. I have tried many combinations but the motor is not rotating. The sync signal can be routed from GPIO matrix or from MCPWM Timer event. This closed loop control for BLDC motor system could be used in drilling machines, lath machines, spinning machines, elevators and electric bikes. Group of supported MCPWM capture event callbacks. Servo Motor A servo motor consists of a DC motor, reduction gearbox, positional feedback device and some form of error correction. One generator can set multiple actions on different timer events, by calling mcpwm_generator_set_actions_on_timer_event() with variable number of action configurations. See MCPWM Sync Sources for how to create a sync source object. the input sync signal will be routed to its sync output). There is also another set of three wires coming out of the ESC and that's the signal line, +5V and ground. The ID should belong to [0, SOC_MCPWM_GROUPS - 1] range. Help macros to construct a mcpwm_gen_compare_event_action_t entry. [ (from Espressif documentation) The capture channel is not enabled after allocation by mcpwm_new_capture_channel(). We are using a BLDC motor of rating Model: A2212/6T RPM/V: 2200 kV Current: 12 A/60 s The MCPWM group has a dedicated timer which is used to capture the timestamp when specific event occurred. Last but not least, to allocate a software sync source, you can call mcpwm_new_soft_sync_src() function, with configuration structure mcpwm_soft_sync_config_t as the parameter. Speed Control of DC Motor using Arduino. If the hold_on is false, the force level can be overridden by the next event action. My idea is to utilise the additional "dead-time" that you get with 6xPWM to hopefully better control the motor. The period of the PWM waveform is determined by the timers period and count mode. The configuration structure is defined as: mcpwm_generator_config_t::gen_gpio_num sets the GPIO number used by the generator. This is an aggregation version of mcpwm_generator_set_action_on_timer_event, which allows user to set multiple actions in one call. The mcpwm_new_operator()() will return a pointer to the allocated operator object if the allocation succeeds. Commutation for BLDC motors are a six-step process. Currently this configuration structure is left for future purpose. Generator action on specific brake event. The capture consists one dedicated timer and several independent channels. This will allow the interrupt to run while the cache is disabled but will come at the cost of increased IRAM consumption. Growing need for high productivity is placing new demands on mechanisms connected with electrical motors. mcpwm_capture_timer_sync_phase_config_t::direction sets the count direction when the sync signal is taken. The way that MCPWM operator reacts to the fault is called Brake. This library can control a many types of servos. Each submodule has its own resource allocation, which is described in the following sections. $9.86. See MCPWM Sync Sources for how to create a sync source object. Three phase motor control using the MCPWM 6x Mosfets and Smart Driver SPI for the dual Absolute Magnetic Encoder I2C for the OLED Bluetooth, Wifi, CAN, ESP-NOW or serial for communications Current, Voltage and Temperature monitoring IMG_4840s.jpg ESP-32 DRV4_0.jpg You do not have the required permissions to view the files attached to this post. The motor we'll control is connected to the motor A output pins, so we need to wire the ENABLEA, INPUT1 and INPUT2 pins of the motor driver to the ESP32. These IO control functions are as follows: The factory functions like mcpwm_new_timer() are guaranteed to be thread safe by the driver, which means, you can call it from different RTOS tasks without protection by extra locks. Try to make the operator recover from fault. Set your budget and timeframe . Other functions that are not related to Resource Allocation, are not thread safe. Set generator action on MCPWM brake event. Activate the software sync, trigger the sync event for once. When a sync signal is taken by the MCPWM timer, the timer will be forced into a predefined phase, where the phase is determined by count value and count direction. Please note, GPIO fault located in different groups are totally independent, i.e. We can shut down the PWM output immediately or regulate the PWM output cycle by cycle, depends on how critical the fault is. 1. On the contrary, calling mcpwm_del_timer() function will free the allocated timer object. Specifically, when there are no memory left for the sync source object, this function will return ESP_ERR_NO_MEM error. Internally, this function will: switch the timer state from init to enable. The callback function will provide event specific data of type mcpwm_capture_event_data_t, so that you can get the edge of the capture signal in mcpwm_capture_event_data_t::cap_edge and the count value of that moment in mcpwm_capture_event_data_t::cap_value. More by the author: This is a modification and addition to my instructable.com tutorials on DC Motors, and it also includes some information from my tutorial on the "ESP32 Tutorial: Touch, Hall, I2C, PWM, ADC, & DAC". How it works: When the BLDC motor rotates, each winding (3 windings) generates BEMF opposes the main voltage. ESP-32 BLDC Robot Actuator Controller Back to overview ESP-32 WROOM-32D has Three phase Centre Aligned MC-PWM, Dual SPI, I2C, 2MHz ADC, UART and CAN. But then I've also seen controllers like this and then . On the contrary, calling mcpwm_del_sync_src() function will free the allocated sync source object, this function works for all types of sync sources. A new file will open. By default, the MCPWM interrupt will be deferred when the Cache is disabled for reasons like writing/erasing Flash. ev_act [in] MCPWM timer event action, can be constructed by MCPWM_GEN_TIMER_EVENT_ACTION helper macro, ESP_OK: Set generator action successfully, ESP_ERR_INVALID_ARG: Set generator action failed because of invalid argument, ESP_ERR_INVALID_STATE: Set generator action failed because of timer is not connected to operator, ESP_FAIL: Set generator action failed because of other error. MCPWM Comparator: The compare module takes the time-base count value as input, and continuously compare to the threshold value that configured by user. About this item. Otherwise, it will return error code ESP_ERR_INVALID_STATE. If your application requires accurate speed control and your motor does not have Hall-effect sensors (many BLDC motors do), then this simplified circuit is not suitable for your application. The step size of each count tick equals to (1 / resolution_hz) seconds, Whether to update period when timer counts to zero, The sync event source. Each bridge arm has two power electronic devices, such as MOSFET, IGBT, etc. The configuration structure is defined as: mcpwm_capture_channel_config_t::gpio_num sets the GPIO number used by the capture channel. Specifically, when there are no free capture channel left in the capture timer, this function will return ESP_ERR_NOT_FOUND error. The motor turns on reliably at about 1050 with very low rpms, and runs up to a measured 8650 rpm at 1400. Specifically, when there are no more free operators in the MCPWM group, this function will return ESP_ERR_NOT_FOUND error. However, the driver can prevent the system from changing APB frequency by acquiring a power management lock of type ESP_PM_APB_FREQ_MAX. Otherwise, it will return error code. MCPWM comparator event callback function. The operator handle is created by mcpwm_new_operator()(). The parameter user_data of mcpwm_comparator_register_event_callbacks() function is used to save users own context, it will be passed to the callback function directly. For industrial usage Infineon adds to the 3-phase brushless DC motor . Each channel is connected to the GPIO, a pulse on the GPIO will trigger the capture timer to store the time-base count value and then notify the user by interrupt. To allocate a GPIO sync source, you can call mcpwm_new_gpio_sync_src() function, with configuration structure mcpwm_gpio_sync_src_config_t as the parameter. No attempt has been made to support multiple servos per channel. counter is empty), MCPWM timer counts to peak (i.e. Specifically, setting both of them to zero means to bypass the dead-time module. Please note, GPIO sync source located in different groups are totally independent, i.e. The capture timer is usually connected with several capture channels, please refer to MCPWM Capture Timer and Channels for resource allocation. mcpwm_timer_config_t::clk_src sets the clock source of the timer. The duty cycle of the PWM waveform is determined by the generators various action combinations. MCPWM comparator event data, fed by driver, User data, set in mcpwm_comparator_register_event_callbacks(), User data, set in mcpwm_capture_channel_register_event_callbacks(), MCPWM timer counts to zero (i.e. Help macros to construct a mcpwm_gen_brake_event_action_t entry. Please always check the return value when doing Resource Allocation. mcpwm_gen_compare_event_action_t::action specifies the generator action to be taken. In this case we do not use the red wire of the ESC because it supplies 5v and our NodeMCU works at 3.3v, so we can damage it. Looking to make some money? It's powered by an ESP32 (ESP32-PICO-V3-02) running Arduino, using the SimpleFOC library for closed-loop motor control with an MT6701 magnetic encoder (it's a seriously awesome encoder chip; way better than the common AS5600 or TLV493d options). mcpwm_generator_config_t::io_loop_back sets whether to enable the loop back mode. will remain unchanged until manually remove the force level), ESP_OK: Set force level for MCPWM generator successfully, ESP_ERR_INVALID_ARG: Set force level for MCPWM generator failed because of invalid argument, ESP_FAIL: Set force level for MCPWM generator failed because of other error. Specifically, if a sync source has been allocated from the same timer before, this function will return ESP_ERR_INVALID_STATE error. Shipping, returns & payments. mcpwm_new_soft_fault() function will return a pointer to the allocated fault object if the allocation succeeds. Content Topic Group. The compare value shouldnt exceed timers count peak, otherwise, the compare event will never got triggered. ESP_OK: Enable MCPWM capture channel successfully, ESP_ERR_INVALID_ARG: Enable MCPWM capture channel failed because of invalid argument, ESP_ERR_INVALID_STATE: Enable MCPWM capture channel failed because the channel is already enabled, ESP_FAIL: Enable MCPWM capture channel failed because of other error, ESP_OK: Disable MCPWM capture channel successfully, ESP_ERR_INVALID_ARG: Disable MCPWM capture channel failed because of invalid argument, ESP_ERR_INVALID_STATE: Disable MCPWM capture channel failed because the channel is not enabled yet, ESP_FAIL: Disable MCPWM capture channel failed because of other error. mcpwm_carrier_config_t::invert_before_modulate and mcpwm_carrier_config_t::invert_after_modulate: Set whether to invert the carrier output before and after modulation. The update time for the compare value is set by mcpwm_comparator_config_t::update_cmp_on_tez or mcpwm_comparator_config_t::update_cmp_on_tep or mcpwm_comparator_config_t::update_cmp_on_sync. The ID should belong to [0, SOC_MCPWM_GROUPS - 1] range. The first pulse duration cant be zero, and it has to be at least one period of the carrier. ISR callback function which would be invoked when counter reaches compare value, components/driver/mcpwm/include/driver/mcpwm_gen.h. ev_act [in] MCPWM brake event action list, must be terminated by MCPWM_GEN_BRAKE_EVENT_ACTION_END(), in_generator [in] MCPWM generator, before adding the dead time, out_generator [in] MCPWM generator, after adding the dead time, config [in] MCPWM dead time configuration, ESP_OK: Set dead time for MCPWM generator successfully, ESP_ERR_INVALID_ARG: Set dead time for MCPWM generator failed because of invalid argument, ESP_FAIL: Set dead time for MCPWM generator failed because of other error, The GPIO number used to output the PWM signal, Whether to invert the PWM signal (done by GPIO matrix), For debug/test, the signal output from the GPIO will be fed to the input path as well. Specifically, if this is set to NULL, the driver will disable the sync feature for the MCPWM timer. mcpwm_operator_config_t::update_dead_time_on_tez sets whether to update the dead time when the timer counts to zero. This function will lazy install interrupt service for the MCPWM fault, whereas the service can only be removed in mcpwm_del_fault. Advantages and disadvantages of brushless dc motor system closed May 6, 2021, 9:44am #12 We develop customized motor control solutions to operate modern electric vehicle powertrains cutting across motor types such as BLDC, PMSM, SRM and induction motors. There are things that I do not need and things I want to be added. If you have some function that should be called when this event happens, you should hook your function to the interrupt service routine by calling mcpwm_operator_register_event_callbacks(). Please note, the argument list of mcpwm_generator_set_actions_on_brake_event() must be terminated by MCPWM_GEN_BRAKE_EVENT_ACTION_END. To recover from fault or escape from trip, you make sure the fault signal has dissappeared already. You can set the compare value for the MCPWM comparator at runtime by calling mcpwm_comparator_set_compare_value(). Integrated bootstrap diodes are used to supply the . Connect MCPWM operator and timer, so that the operator can be driven by the timer. You can allocate a MCPWM comparator object by calling mcpwm_new_comparator() function, with a MCPWM operator handle and configuration structure mcpwm_comparator_config_t as the parameter. This section will demonstrate the classical PWM waveforms that can be generated by the pair of the generators. but it didnt completed the whole 12 turns. The mcpwm_capture_channel_trigger_soft_catch() is provided for that purpose. Coupling of non alternating signals with a transformer is problematic, so the signals are modulated by the carrier submodule to create an AC waveform, to make the coupling possible. BOOSTXL-DRV8301 Motor Drive BoosterPack featuring DRV8301 and NexFET MOSFETs. The configuration structure is defined as: mcpwm_operator_config_t::group_id specifies the MCPWM group ID. This function will lazy install interrupt service for the MCPWM capture channel, whereas the service can only be removed in mcpwm_del_capture_channel. Get same day shipping on all orders. I'm trying to figure out how to control the speed of a 400-watt, 3000RPM, 48V BLDC with Hall sensors with a Raspberry Pi 3. MCPWM software fault configuration structure. Please refer to the [TRM] for details. Specifically, when there are no more free timers in the MCPWM group, this function will return ESP_ERR_NOT_FOUND error. The fact is that, although the PWM wave shows it is turning off the switch, but the MOSFET still needs a small time window to make that happen. You can allocate a MCPWM operator object by calling mcpwm_new_operator()() function, with a configuration structure mcpwm_operator_config_t as the parameter. 0, 4/2010 Freescale Semiconductor, Inc. 3 System Description. Make sure the operator has connected to one MCPWM timer already by mcpwm_operator_connect_timer(). The sync phase configuration is defined in mcpwm_timer_sync_phase_config_t structure: mcpwm_timer_sync_phase_config_t::sync_src sets the sync signal source. Group of supported MCPWM operator event callbacks. MCPWM capture timer configuration structure. MCPWM software sync configuration structure. It is for debugging purposes only. The action configuration is defined in mcpwm_gen_timer_event_action_t: mcpwm_gen_timer_event_action_t::direction specific the timer direction. Unlike an H bridge, this circuit configuration has only two switches - one high-side and one low-side transistor. mcpwm_capture_timer_sync_phase_config_t::count_value sets the count value to load when the sync signal is taken. Otherwise, it will return error code. Evaluation board. Outrunner bldc motor simulation winding schema. The first call to this function needs to be before the call to mcpwm_capture_channel_enable, ESP_ERR_INVALID_STATE: Set event callbacks failed because the channel is not in init state, ESP_OK: Trigger software catch successfully, ESP_ERR_INVALID_ARG: Trigger software catch failed because of invalid argument, ESP_ERR_INVALID_STATE: Trigger software catch failed because the channel is not enabled yet, ESP_FAIL: Trigger software catch failed because of other error.
