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ESP32: Use SOC_RMT_MEM_WORDS_PER_CHANNEL to determine if the RMT hardware can handle DCC

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This commit is contained in:
Harald Barth 2024-01-07 22:22:38 +01:00
parent 74f7af1675
commit 4a3d3228a9
2 changed files with 39 additions and 19 deletions
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48
DCCRMT.cpp
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@ -1,5 +1,5 @@
/*
* © 2021-2022, Harald Barth.
* © 2021-2024, Harald Barth.
*
* This file is part of DCC-EX
*
@ -25,6 +25,18 @@
#include "DCCWaveform.h" // for MAX_PACKET_SIZE
#include "soc/gpio_sig_map.h"
// check for right type of ESP32
#include "soc/soc_caps.h"
#ifndef SOC_RMT_MEM_WORDS_PER_CHANNEL
#error This symobol should be defined
#endif
#if SOC_RMT_MEM_WORDS_PER_CHANNEL < 64
#warning This is not an ESP32-WROOM but some other unsupported variant
#warning You are outside of the DCC-EX supported hardware
#endif
static const byte RMT_CHAN_PER_DCC_CHAN = 2;
// Number of bits resulting out of X bytes of DCC payload data
// Each byte has one bit extra and at the end we have one EOF marker
#define DATA_LEN(X) ((X)*9+1)
@ -75,12 +87,30 @@ void IRAM_ATTR interrupt(rmt_channel_t channel, void *t) {
RMTChannel::RMTChannel(pinpair pins, bool isMain) {
byte ch;
byte plen;
// Below we check if the DCC packet actually fits into the RMT hardware
// Currently MAX_PACKET_SIZE = 5 so with checksum there are
// MAX_PACKET_SIZE+1 data packets. Each need DATA_LEN (9) bits.
// To that we add the preamble length, the fencepost DCC end bit
// and the RMT EOF marker.
// SOC_RMT_MEM_WORDS_PER_CHANNEL is either 64 (original WROOM) or
// 48 (all other ESP32 like the -C3 or -S2
// The formula to get the possible MAX_PACKET_SIZE is
//
// ALLOCATED = RMT_CHAN_PER_DCC_CHAN * SOC_RMT_MEM_WORDS_PER_CHANNEL
// MAX_PACKET_SIZE = floor((ALLOCATED - PREAMBLE_LEN - 2)/9 - 1)
//
if (isMain) {
ch = 0;
plen = PREAMBLE_BITS_MAIN;
static_assert (DATA_LEN(MAX_PACKET_SIZE+1) + PREAMBLE_BITS_MAIN + 2 <= RMT_CHAN_PER_DCC_CHAN * SOC_RMT_MEM_WORDS_PER_CHANNEL,
"Number of DCC packet bits greater than ESP32 RMT memory available");
} else {
ch = 2;
ch = RMT_CHAN_PER_DCC_CHAN; // number == offset
plen = PREAMBLE_BITS_PROG;
static_assert (DATA_LEN(MAX_PACKET_SIZE+1) + PREAMBLE_BITS_PROG + 2 <= RMT_CHAN_PER_DCC_CHAN * SOC_RMT_MEM_WORDS_PER_CHANNEL,
"Number of DCC packet bits greater than ESP32 RMT memory available");
}
// preamble
@ -123,20 +153,10 @@ RMTChannel::RMTChannel(pinpair pins, bool isMain) {
config.channel = channel = (rmt_channel_t)ch;
config.clk_div = RMT_CLOCK_DIVIDER;
config.gpio_num = (gpio_num_t)pins.pin;
config.mem_block_num = 2; // With longest DCC packet 11 inc checksum (future expansion)
// number of bits needed is 22preamble + start +
// 11*9 + extrazero + EOT = 124
// 2 mem block of 64 RMT items should be enough
config.mem_block_num = RMT_CHAN_PER_DCC_CHAN;
// use config
ESP_ERROR_CHECK(rmt_config(&config));
addPin(pins.invpin, true);
/*
// test: config another gpio pin
gpio_num_t gpioNum = (gpio_num_t)(pin-1);
PIN_FUNC_SELECT(GPIO_PIN_MUX_REG[gpioNum], PIN_FUNC_GPIO);
gpio_set_direction(gpioNum, GPIO_MODE_OUTPUT);
gpio_matrix_out(gpioNum, RMT_SIG_OUT0_IDX, 0, 0);
*/
// NOTE: ESP_INTR_FLAG_IRAM is *NOT* included in this bitmask
ESP_ERROR_CHECK(rmt_driver_install(config.channel, 0, ESP_INTR_FLAG_LOWMED|ESP_INTR_FLAG_SHARED));

8
DCCWaveform.h
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@ -2,7 +2,7 @@
* © 2021 M Steve Todd
* © 2021 Mike S
* © 2021 Fred Decker
* © 2020-2021 Harald Barth
* © 2020-2024 Harald Barth
* © 2020-2021 Chris Harlow
* All rights reserved.
*
@ -33,9 +33,9 @@
// Number of preamble bits.
const int PREAMBLE_BITS_MAIN = 16;
const int PREAMBLE_BITS_PROG = 22;
const byte MAX_PACKET_SIZE = 5; // NMRA standard extended packets, payload size WITHOUT checksum.
const byte PREAMBLE_BITS_MAIN = 16;
const byte PREAMBLE_BITS_PROG = 22;
const byte MAX_PACKET_SIZE = 5; // NMRA standard extended packets, payload size WITHOUT checksum.
// The WAVE_STATE enum is deliberately numbered because a change of order would be catastrophic