main: commit first working firmware
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729e73e705
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243
main.c
243
main.c
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@ -1,5 +1,5 @@
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/* firmware template for STM8S microcontroller
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* Copyright (C) 2019-2020 King Kévin <kingkevin@cuvoodoo.info>
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/* firmware for STM8S-microcontroller-based HDMI firewall programmer
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* Copyright (C) 2019-2021 King Kévin <kingkevin@cuvoodoo.info>
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* SPDX-License-Identifier: GPL-3.0-or-later
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*/
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#include <stdint.h>
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@ -8,8 +8,47 @@
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#include "stm8s.h"
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#include "main.h"
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#include "i2c_master.h"
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#include "eeprom_blockprog.h"
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// blink RUN LED to show error
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static bool led_error = false;
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// set when the button is pressed
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static volatile bool rw_button_pressed = false;
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// AWU tick count
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static volatile uint8_t awu_tick = 0;
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// to store the current E-EDID (EDID + extension)
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static uint8_t edid[256];
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// function RAM (code in RAM)
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uint8_t f_ram[112 + 5]; // use RAM_SEG size in main.map (plus some margin)
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// function for saving EDID + extension to EEPROM, to put in RAM
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bool (*ram_eeprom_blockprog)(const uint8_t* data, uint16_t length);
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// size of RAM segment
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volatile uint8_t RAM_SEG_LEN;
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// get the size of the RAM segment
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inline void get_ram_section_length() {
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__asm__("mov _RAM_SEG_LEN, #l_RAM_SEG");
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}
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// copy functions to RAM
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bool ram_cpy() {
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get_ram_section_length();
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if (RAM_SEG_LEN > ARRAY_LENGTH(f_ram)) {
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return false;
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}
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for (uint8_t i = 0; i < RAM_SEG_LEN; i++) {
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f_ram[i] = ((uint8_t *)eeprom_blockprog)[i];
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}
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ram_eeprom_blockprog = (bool (*)(const uint8_t* data, uint16_t length)) &f_ram;
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return true;
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}
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// blocking wait (in 10 us steps, up to UINT32_MAX / 10)
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static void wait_10us(uint32_t us10)
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@ -18,6 +57,110 @@ static void wait_10us(uint32_t us10)
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for (volatile uint32_t t = 0; t < us10; t++); // burn energy
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}
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// verify (E-)EDID checksums
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// the sum of the bytes (including checksum at the end) must be 0
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static bool checksum_ok(const uint8_t* data, uint16_t length)
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{
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uint8_t checksum = 0;
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for (uint16_t i = 0; i < length; i++) {
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checksum += data[i];
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}
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return (0 == checksum);
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}
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// return if the current EDID is valid
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/* from HDMI 1.3a specification
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* All Sinks shall contain an CEA-861-D compliant E-EDID data structure.
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* A Source shall read the EDID 1.3 and first CEA Extension to determine the capabilities supported
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by the Sink.
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* The first 128 bytes of the E-EDID shall contain an EDID 1.3 structure. The contents of this
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structure shall also meet the requirements of CEA-861-D.
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*
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* HDMI 2.1 uses CTA-861-G
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* this uses EDID 1.4 structure
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* EDID 1.3/1.4 is 128 bytes long, and can point to 128 bytes extension
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* EDID 2.0 with its 256 bytes does not seem to be used in HDMI at all
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* DisplayID with its variable-length structure meant to replace E-EDID only seems to be used in DisplayPort
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* I have no idea how more than 1 extension is supported since technically the ROM is limited to 256 bytes
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*/
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static uint16_t edid_length(void)
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{
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// check EDID 1.3/1.4 fixed pattern header
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if (0x00 != edid[0] || 0xff != edid[1] || 0xff != edid[2] || 0xff != edid[3] || 0xff != edid[4] || 0xff != edid[5] || 0xff != edid[6] || 0x00 != edid[7]) {
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return 0;
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}
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if (1 == edid[18]) { // EDID 1.3/1.4 128-byte structure
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if (checksum_ok(&edid[0], 128)) {
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if (0 == edid[126]) { // no extension
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return 128;
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} else { // extension available
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// the usual extension is CEA EDID Timing Extension (with extension tag 02), but we allow others
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// no idea how more than 1 extension is supported
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if (checksum_ok(&edid[128], 128)) {
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return 256;
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} else {
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return 0; // EDID is broken
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}
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}
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} else {
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return 0;
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}
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} else if (2 == edid[18]) { // EDID 2.0 256-byte structure
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if (checksum_ok(&edid[0], 256)) {
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return 256;
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} else {
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return 0;
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}
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}
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return 0;
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}
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// load EDID + extension from EEPROM
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static void load_edid(void)
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{
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for (uint16_t i = 0; i < ARRAY_LENGTH(edid); i++) {
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edid[i] = *(uint8_t*)(EEPROM_ADDR + i);
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}
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}
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// save EDID + extension in EEPROM
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static bool save_edid(void)
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{
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return ram_eeprom_blockprog(edid, edid_length());
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}
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// read EDID from I²C memory
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// return if succeeded
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static bool read_edid(void)
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{
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const uint8_t address[] = {0};
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if (!i2c_master_setup(false)) {
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return false;
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}
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if (I2C_MASTER_RC_NONE != i2c_master_address_read(I2C_SLAVE, false, address, ARRAY_LENGTH(address), edid, ARRAY_LENGTH(edid))) {
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return false;
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}
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i2c_master_release(); // release I²C again
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return true;
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}
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// write EDID to I²C memory
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// return if succeeded
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static bool write_edid(void)
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{
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const uint8_t address[] = {0};
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if (!i2c_master_setup(false)) {
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return false;
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}
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if (I2C_MASTER_RC_NONE != i2c_master_address_write(I2C_SLAVE, false, address, ARRAY_LENGTH(address), edid, edid_length())) {
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return false;
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}
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i2c_master_release(); // release I²C again
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return true;
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}
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void main(void)
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{
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sim(); // disable interrupts (while we reconfigure them)
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@ -26,6 +169,24 @@ void main(void)
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CLK->CKDIVR.fields.CPUDIV = CLK_CKDIVR_CPUDIV_DIV0; // don't divide CPU frequency to 16 MHz
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while (!CLK->ICKR.fields.HSIRDY); // wait for internal oscillator to be ready
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// save power by disabling unused peripheral
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CLK_PCKENR1 = CLK_PCKENR1_I2C; // keep I²C
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CLK_PCKENR2 = CLK_PCKENR2_AWU; // keep AWU
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// configure LEDs
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EDID_LED_PORT->DDR.reg |= EDID_LED_PIN; // switch pin to output
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EDID_LED_PORT->CR1.reg &= ~EDID_LED_PIN; // use in open-drain mode
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edid_led_off(); // start with LED off
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RUN_LED_PORT->DDR.reg |= RUN_LED_PIN; // switch pin to output
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RUN_LED_PORT->CR1.reg &= ~RUN_LED_PIN; // use in open-drain mode
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run_led_off(); // start with LED off
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// configure read/write button
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RW_BUTTON_PORT->DDR.reg &= ~RW_BUTTON_PIN; // switch pin to input
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RW_BUTTON_PORT->CR1.reg |= RW_BUTTON_PIN; // pull up
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RW_BUTTON_PORT->CR2.reg |= RW_BUTTON_PIN; // enable external interrupt
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EXTI->CR1.fields.PDIS = EXTI_FALLING_EDGE; // interrupt only on falling edges (WARNING hard coded port)
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// configure auto-wakeup (AWU) to be able to refresh the watchdog
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// 128 kHz LSI used by default in option bytes CKAWUSEL
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// we skip measuring the LS clock frequency since there is no need to be precise
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@ -33,6 +194,9 @@ void main(void)
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AWU->APR.fields.APR = 0x3e; // set time to 256 ms
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AWU_CSR |= AWU_CSR_AWUEN; // enable AWU (start only when entering wait or active halt mode)
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// load function in RAM
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ram_cpy();
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// configure independent watchdog (very loose, just it case the firmware hangs)
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IWDG->KR.fields.KEY = IWDG_KR_KEY_REFRESH; // reset watchdog
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IWDG->KR.fields.KEY = IWDG_KR_KEY_ENABLE; // start watchdog
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IWDG->PR.fields.PR = IWDG_PR_DIV256; // set prescale to longest time (1.02s)
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IWDG->KR.fields.KEY = IWDG_KR_KEY_REFRESH; // reset watchdog
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// erase saved EDID when button is pressed on boot
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if (0 == (RW_BUTTON_PORT->IDR.reg & RW_BUTTON_PIN)) { // button is pressed while booting
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for (uint16_t i = 0; i < ARRAY_LENGTH(edid); i++) {
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edid[i] = 0; // create empty EDID
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}
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ram_eeprom_blockprog(edid, ARRAY_LENGTH(edid)); // erase EDID
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}
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load_edid(); // load EDID from EEPROM
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bool edid_valid = (0 != edid_length()); // verify if EDID is valid
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rim(); // re-enable interrupts
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bool action = false; // if an action has been performed
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while (true) {
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IWDG_KR = IWDG_KR_KEY_REFRESH; // reset watchdog
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// handle button press
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if (rw_button_pressed) {
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wait_10us(100); // wait 1 ms for the noise to be gone
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if (0 == (RW_BUTTON_PORT->IDR.reg & RW_BUTTON_PIN)) { // ensure the button is pressed (the pull-up is really weak)
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wait_10us(10000); // debounce for 100 ms
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uint8_t press_duration = 1; // start counting how long the button is pressed
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while (0 == (RW_BUTTON_PORT->IDR.reg & RW_BUTTON_PIN)) { // wait until button is depressed
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wait_10us(10000); // wait for 100 ms
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press_duration++;
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IWDG_KR = IWDG_KR_KEY_REFRESH; // reset watchdog
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}
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led_error = false; // reset error state
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if (press_duration < 30) { // less than 3 sec
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run_led_on(); // indicate we started
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if (read_edid()) { // read EDID from I²C
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edid_valid = (0 != edid_length()); // verify if EDID is valid
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if (edid_valid) { // read EDID is valid
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IWDG_KR = IWDG_KR_KEY_REFRESH; // reset watchdog
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led_error = !save_edid(); // save to EEPROM
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IWDG_KR = IWDG_KR_KEY_REFRESH; // reset watchdog
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} else { // read EDID is not valid
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led_error = true; // indicate read error
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load_edid(); // re-load EDID from EEPROM
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edid_valid = (0 != edid_length()); // verify if EDID is valid
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}
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} else { // read error
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led_error = true; // indicate read error
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load_edid(); // re-load EDID from EEPROM
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edid_valid = (0 != edid_length()); // verify if EDID is valid
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}
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i2c_master_release(); // release I²C again
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} else { // button pressed > 3s
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run_led_on(); // indicate we started
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if (edid_valid) {
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led_error = !write_edid(); // write EDID to I²C EEPROM
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} else {
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led_error = true; // we can't program an invalid EDID
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}
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}
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}
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action = true; // remember we performed an action
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rw_button_pressed = false; // clear flag
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}
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// update LED
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if ((awu_tick & 0x7) < 4) { // on period of blink (every second)
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edid_led_on(); // on period
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if (led_error) {
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run_led_on(); // start blinking
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}
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} else {
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if (!edid_valid) { // EDID not valid
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edid_led_off(); // blink to let user know
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}
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if (led_error) {
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run_led_off(); // blink to indicate error
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}
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}
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if (action) { // something has been performed, check if other flags have been set meanwhile
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action = false; // clear flag
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} else { // nothing down
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wfi(); // go to sleep (wait for any interrupt, including periodic AWU)
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wfi(); // go to sleep (wait for any interrupt, also starting AWU)
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}
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}
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}
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@ -55,5 +286,11 @@ void main(void)
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void awu(void) __interrupt(IRQ_AWU) // auto wakeup
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{
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volatile uint8_t awuf = AWU_CSR; // clear interrupt flag by reading it (reading is required, and volatile prevents compiler optimization)
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awu_tick++; // increment tick count
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// let the main loop kick the dog
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}
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void rw_button_isr(void) __interrupt(IRQ_EXTI3) // button pressed
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{
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rw_button_pressed = true; // notify main loop
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}
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35
main.h
35
main.h
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@ -1,2 +1,37 @@
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// get length of array
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#define ARRAY_LENGTH(x) (sizeof(x) / sizeof((x)[0]))
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// LED to indicate valid EDID
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// sink to witch on
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// off = firmware not running
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// on = valid EDID
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// blink = no valid EDID
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#define EDID_LED_PORT GPIO_PD
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#define EDID_LED_PIN PD4
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#define edid_led_on() {EDID_LED_PORT->ODR.reg &= ~EDID_LED_PIN;}
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#define edid_led_off() {EDID_LED_PORT->ODR.reg |= EDID_LED_PIN;}
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#define edid_led_toggle() {EDID_LED_PORT->ODR.reg ^= EDID_LED_PIN;}
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// LED to indicate operation read/write result
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// sink to switch on
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// off = no operation started
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// on = operation succeeded
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// blink = operation failed
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#define RUN_LED_PORT GPIO_PD
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#define RUN_LED_PIN PD6
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#define run_led_on() {RUN_LED_PORT->ODR.reg &= ~RUN_LED_PIN;}
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#define run_led_off() {RUN_LED_PORT->ODR.reg |= RUN_LED_PIN;}
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#define run_led_toggle() {RUN_LED_PORT->ODR.reg ^= RUN_LED_PIN;
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// button to start read/write operation
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// press shorts it to ground
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// short press = read EDID
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// long press (> 3s) = write EDID
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#define RW_BUTTON_PORT GPIO_PD
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#define RW_BUTTON_PIN PD3
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// start address of EEPROM
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#define EEPROM_ADDR 0x4000
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// address of I²C EEPROM slave device containing EDID information
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#define I2C_SLAVE 0x50
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