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October 21, 2022 11:08
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Raspberry Pi Pico Micropython PWM DMA CHAIN LED fade
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from uctypes import * | |
from machine import Pin, PWM, mem32 | |
from sys import byteorder | |
# control register structure | |
DMA_CTRL_LAYOUT = { | |
"AHB_ERROR": 31<<BF_POS | 1<<BF_LEN | BFUINT32, | |
"READ_ERROR": 30<<BF_POS | 1<<BF_LEN | BFUINT32, | |
"WRITE_ERROR": 29<<BF_POS | 1<<BF_LEN | BFUINT32, | |
"BUSY": 24<<BF_POS | 1<<BF_LEN | BFUINT32, | |
"SNIFF_EN": 23<<BF_POS | 1<<BF_LEN | BFUINT32, | |
"BSWAP": 22<<BF_POS | 1<<BF_LEN | BFUINT32, | |
"IRQ_QUIET": 21<<BF_POS | 1<<BF_LEN | BFUINT32, | |
"TREQ_SEL": 15<<BF_POS | 6<<BF_LEN | BFUINT32, | |
"CHAIN_TO": 11<<BF_POS | 4<<BF_LEN | BFUINT32, | |
"RING_SEL": 10<<BF_POS | 1<<BF_LEN | BFUINT32, | |
"RING_SIZE": 6<<BF_POS | 4<<BF_LEN | BFUINT32, | |
"INCR_WRITE": 5<<BF_POS | 1<<BF_LEN | BFUINT32, | |
"INCR_READ": 4<<BF_POS | 1<<BF_LEN | BFUINT32, | |
"DATA_SIZE": 2<<BF_POS | 2<<BF_LEN | BFUINT32, | |
"HIGH_PRIORITY": 1<<BF_POS | 1<<BF_LEN | BFUINT32, | |
"EN": 0<<BF_POS | 1<<BF_LEN | BFUINT32 | |
} | |
DMA_BASE = const(0x5000_0000) | |
# channel offset | |
DMA_CH = 0x040 | |
# alias CSRs offset address | |
DMA_0_READ_ADDR = const(0x000) | |
DMA_0_WRITE_ADDR = const(0x004) | |
DMA_0_TRANS_COUNT = const(0x008) | |
DMA_0_CTRL_TRIG = const(0x00c) | |
DMA_1_CTRL = const(0x010) | |
DMA_3_READ_ADD_TRIG = const(0x03c) | |
# raw intrrupt status register | |
DMA_INTR = const(0x400) | |
PWM_BASE = const(0x4005_0000) | |
#channel offset (PWM_BASE + (CH * ch) + CC) | |
PWM_CH = const(0x14) | |
PWM_CSR = const(0x00) # control and status register | |
PWM_DIV = const(0x04) # divider | |
PWM_CTR = const(0x08) # counter | |
PWM_CC = const(0x0c) # counter compare | |
PWM_TOP = const(0x10) # counter wrap value | |
@micropython.viper | |
def fade(): | |
fade = bytearray(4*256) | |
p = ptr32(fade) | |
for i in range(0, 256, 1): | |
p[i] = uint(i * i << 16) # cc channel B | |
return fade | |
fade = fade() | |
# pwm slice 4 | |
DREQ_PWM_WRAP4 = 28 | |
pwm_ch = PWM_BASE + (PWM_CH * 4) | |
pwm_cc = pwm_ch + PWM_CC | |
# PWM slice=4, channel=1 | |
led = PWM(Pin(25)) | |
# clkdiv 8.0 | |
mem32[pwm_ch + PWM_DIV] = (0x8 << 4) | |
# start pwm | |
mem32[pwm_ch + PWM_CSR] |= 1 | |
dma_ch_pwm = DMA_BASE + (DMA_CH * 1) | |
dma_ch_config = DMA_BASE + (DMA_CH * 2) | |
config = addressof(fade).to_bytes(4, byteorder) | |
mem32[dma_ch_config + DMA_0_READ_ADDR] = addressof(config) | |
mem32[dma_ch_config + DMA_0_WRITE_ADDR] = dma_ch_pwm + DMA_3_READ_ADD_TRIG | |
mem32[dma_ch_config + DMA_0_TRANS_COUNT] = 1 | |
ctrl = struct(dma_ch_config + DMA_1_CTRL, DMA_CTRL_LAYOUT) | |
ctrl.TREQ_SEL = 0x3f # permanent request | |
ctrl.CHAIN_TO = (dma_ch_pwm - DMA_BASE) // DMA_CH | |
ctrl.INCR_WRITE = 0 | |
ctrl.INCR_READ = 0 | |
ctrl.DATA_SIZE = 0x2 # SIZE_WORD: 4 bytes | |
ctrl.EN = 1 | |
# dma channel for pwm | |
mem32[dma_ch_pwm + DMA_0_READ_ADDR] = addressof(fade) | |
mem32[dma_ch_pwm + DMA_0_WRITE_ADDR] = pwm_cc | |
mem32[dma_ch_pwm + DMA_0_TRANS_COUNT] = 256 | |
ctrl = struct(dma_ch_pwm + DMA_0_CTRL_TRIG, DMA_CTRL_LAYOUT) | |
ctrl.TREQ_SEL = DREQ_PWM_WRAP4 | |
ctrl.CHAIN_TO = (dma_ch_config - DMA_BASE) // DMA_CH | |
ctrl.INCR_WRITE = 0 | |
ctrl.INCR_READ = 1 | |
ctrl.DATA_SIZE = 0x2 # SIZE_WORD: 4 bytes | |
ctrl.EN = 1 |
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