关于配置Timer为PWM模式,在AM335X Technical Reference Manual的20.1.3.5 Pulse-Width Modulation中有介绍,但客户在使用时反应实际进行编程操作时,存在一些困惑,且starterware中无相关例子可参考。
下面以在linux下的脚本为例,介绍配置步骤,starterware下可以在DTimer的例子中作相应修改。
其配置流程为:(以下是linux下的脚本,在linux下测试过,测试xdma_event_intr0有对应输出。同时说明下devmem2是linux下的读写物理内存的工具而已。)
(1)
# Enable Timer4's clock in CM_PER
# This allows us to access it's control regs
devmem2 0x44e00088 w 0x2
(2)
# Set the Pinmux for Timer4 (0x2 because its mode 2 of this pin)
# Using the pin mux linux driver from the SDK
echo 0x22 > /sys/kernel/debug/omap_mux/xdma_event_intr0
(3)
# Timer configurations.. Stop Timer.
# Auto-Reload
# Compare Mode Enabled
# Trigger set on overflow
# Toggle Mode
devmem2 0x48044038 w 0x1842
(4)
# Write to the CM_DPLL registers to select the clk source
# Selected the clk source for the Timer4
# This should be &= (default 0x12) (writing a 0x2 for 32kHz)
devmem2 0x44e00510 w 0x12
(5)
# Initial count value
devmem2 0x4804403C w 0xFFFFC000
# Set the re-load value
devmem2 0x48044040 w 0xFFFFC000
# Setting a duty cycle
devmem2 0x4804404C w 0xFFFFE000
(6)
# Start Timer
devmem2 0x48044038 w 0x1843