Chapter 4. Software framework
• For the LCD screen driven by the SPI interface, the driver IC generally has built-in GRAM. Thus, the static
pictures can be displayed normally without the ESP continuously outputting the SPI clock, but the pictures
cannot be updated during this period.
Are 9-bit bus and 18-bit color depth supported if I use the ILI9488 LCD screen to test the screen example?
The ILI9488 driver chip can support 9-bit bus and 18-bit color depth. However, Espressif’s driver
can only support 8-bit bus and 16-bit color depth for now. You can modify the driver according to the
ILI9488 datasheet to support 9-bit bus and 18-bit color depth.
4.4.7 LED Control (LEDC)
What is the frequency range for ESP8266 PWM?
The PWM of ESP8266 is realized via software programming, so the maximum CLK value is 1 M limited
by timer. It is recommended to set the frequency to 1 K. The PWM frequency can also be improved by
decreasing the resolution of duty cycle.
Are there any limits on outputting PWM via ESP32 GPIO pins? Can I distribute it to any I/O?
• The ESP32 can output PWM using any GPIO via IO Matrix. Theoretically, the PWM can be distributed to
any I/O except for those that only have input functions (e.g., GPIO34 ~ GPIO39).
• In the actual use, this could also be aected by the limitations of chips and modules, the un-pinned I/Os, ash
occupations and etc.
The PWM of ESP8266 NonOS SDK changes slow. What could be the reasons?
• If you are using the gradient APIs in SDK example/IOT_demo, e.g., light_set_aim or
light_set_aim_r, it will need a gradual process for PWM changes.
• If you need the PWM Duty to take eect immediately after conguration, please call API pwm_set_duty,
and call pwm_start next to make this conguration take eect.
When the LEDC is in decremental fade mode, a duty overow error can occur. How to solve the issue?
When using LEDC, avoid the concurrence of following three cases:
• The LEDC is in decremental fade mode;
• The scale register is set to 1;
• The duty is 2
LEDC_HSTIMERx_DUTY_RES
or 2
LEDC_LSTIMERx_DUTY_RES
.
Espressif Systems 72
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