UART

[中文]

1 Functional Overview

The BK7258 has a total of 2 groups of PWM, with each group having 6 channels.

1. For each group of PWM, only one of the adjacent channels can be independently output ((0,1) adjacent, (2,3) adjacent, (4,5) adjacent), and simultaneous output will cause mutual interference.

2. Each group of PWM can implement 3 complementary outputs, as shown in the table in the overview. Only PWMx’s CH0 and CH1, CH2 and CH3, and CH4 and CH5 can be configured as complementary outputs, with corresponding dead time registers available for configuration. This method is more precise, but the channels are fixed.

3. PWM1’s CH0, CH2, CH4 and PWM2’s CH0, CH2, CH4 can be combined to form a complementary output using any two channels, implementing the complementary function through software. This method is more flexible, but the precision is not as good as the hardware implementation.

4. Additionally, when applying to lamps or motors, it is not recommended to use P8/P22, P9/P23.

The BK7258 has 12 PWM output channels. When outputting, the clock source is 26M, and the period and duty cycle of each channel can be configured. The channels are as follows:

channel	GPIO	channel	GPIO
0	GPIO6/GPIO18	6	GPIO32
1	GPIO7/GPIO19	7	GPIO33
2	GPIO8/GPIO22	8	GPIO34
3	GPIO9/GPIO23	9	GPIO35
4	GPIO24	10	GPIO36
5	GPIO25	11	GPIO37

Note

When supporting multiple GPIOs, please note the default PWM channel corresponding GPIO configuration. The configuration file is located in gpio_map.h, specifically in the GPIO_PWM_MAP_TABLE.

2 Code path

demo path: components\bk_cli\cli_pwm.c

3 CLI Command Overview

Demo Run Dependencies: Macro Configuration:

NAME	Description	File	value
CONFIG_PWM	support PWM	middleware\soc\bk7258\bk7258.defconfig	y

The demo supports the following commands as listed in the table:

Command	Param	Description
pwm_driver init {26M|DCO}	26M|DCO:clk source,default 26M	init the resoure common to all PWM channels
pwm_driver deinit	none	free all resource related to pwm
pwm {chan} init {period_v} {duty_v} [duty2_v][duty3_v]	chan: pwm channel	power up and config the pwm channel, set the period and duty cycle note: this chip supports 3 duty cycle , parameter duty2_v and duty3_v are optional
	period_v:pwm periord
	duty_v: duty cycle
	duty2_v: second level reversal
	duty3_v: third level reversal
pwm {chan} duty {period_v} {duty_v} [duty2_v] [duty3_v]	chan: pwm channel	configure the period and duty cycle. note: parameter duty2_v and duty3_v are option.
	period_v:pwm periord
	duty_v: duty cycl
	duty2_v: second level reversal
	duty3_v: third level reversal
pwm {chan} {start|stop|deinit}	chan: pwm channel	read data_size bytes of data from
	start|stop|deinit:
pwm {chan} signal {low|high}	chan: pwm channel	set the initial signal to high|low
	low|high: initial signal level
pwm_group init {chan1} {chan2} {period} {chan1_duty} {chan2_duty}	chan1: pwm channel	init the PWM group The PWM group is a channel pair that has following attributes: -The period is same -The initial signal level is opposite -Start and stop at the same time
	chan2: pwm channel
	period: pwm periord
	chan1_duty: chan1 duty cycle
	chan2_duty: chan2 duty cycle
pwm_group {start|stop|deinit}	chan: pwm channel	start|stop|deinit the PWM group
	start|stop|deinit:
pwm_group config {group} {period} {chan1_duty} {chan2_duty}	group: pwm channel	Configure the duty and period of a PWM group
	period: pwm periord
	chan1_duty: chan1 duty cycle
	chan2_duty: chan2 duty cycle
pwm_capture {chan} capture_example	chan: pwm channel	calculate the PWM Input Signal’s Period and Duty Cycle
	capture_example

4 Demo Introduction

The demo execution steps are as follows:

1. Prepare a logic analyzer and connect it as follows:

   pwm channel 0----GPIO18
   
   pwm channel 1----GPIO19
   

2. PWM Independent Output Mode

   Initialize the PWM driver:

   pwm_driver init
   

2.1 Ordinary Output

pwm 0 init 200 100 0 0 25 //Duty cycle 50%
pwm 0 start

Waveform as follows:

Figure 1. Outputting a 60% Duty Cycle PWM

Note

According to the parameter configuration, the duty cycle can be adjusted within the same period. However, each adjustment will only take effect in the next period. When setting the PWM init and duty, it must be ensured that period > (D1+D2+D3).