Description
Hardware:
Board: ESP32 DevKit-C
Core Installation/update date: Latest
IDE name: Multiple (ESP-IDF Arduino Component vs. Platform IO)
Flash Frequency: 40Mhz
Upload Speed: 115200
Summary:
I've come across an interesting roadblock. I am not able to change the SPI SLCK frequency in the SPI.cpp library when using arduino-esp32 as a ESP-IDF component. When I use PlatformIO with identical settings, I am able to change the SPI SLKC frequency. It has nothing to do with the U8g2 library as I have tried to hardcode the SPI.cpp frequency values without success.
Description
Arduino-esp32 dictates 4 ways of using the Arduino API with ESP-IDF in the instructions/readme.
Method 1 - Using Arduino API as ESP-IDF Component [This doesn't work]
One of those ways is to use Arduino API as an ESP-IDF component as described here. I managed to add Arduino API to ESP-IDF using this method. Next, I've added a component.mk file to @olikraus's U8g2_Arduino fork.
Component.mk has the following options to add source directors and include files:
COMPONENT_SRCDIRS:=src src/clib
COMPONENT_ADD_INCLUDEDIRS:=src src/clib
Now, U8g2 is a component of ESP-IDF.
Everything works except There is one problem. Usually, I am able to edit the SPI frequency in the u8x2_d_ssd1306_128x64_noname.c,
/* sck_clock_hz = */ 10000000UL,
however, no matter what frequency I set and upload to ESP32, I always get 8MHz as the clock freq. I've validated it using a scope.
I've hardcoded the SPI freq to 10 MHz in the arduino-esp32 SPI.c file and it still doesn't work:
void SPIClass::beginTransaction(SPISettings settings)
{
//check if last freq changed
uint32_t cdiv = spiGetClockDiv(_spi);
if(_freq != settings._clock || _div != cdiv) {
// _freq = settings._clock;
_freq = 10000000UL; // Temporarily hardcoding it for debug purpose. No matter what freq I set here, the default is always 8 MHz.
_div = spiFrequencyToClockDiv(_freq);
}
spiTransaction(_spi, _div, settings._dataMode, settings._bitOrder);
_inTransaction = true;
}
So I tried to use arduino-esp32 using PlatformIO. This problem does not happen when I use Platform IO and downloading latest U8g2 library + arduino-esp32 platform.
Method 2 - Using PlatformIO [This works]
So, I tried the same test as above and I changed the u8x8_d_ssd1306_128x64_noname.c LINE 235 to use 10 MHz as the clock frequency.
/* sck_clock_hz = */ 10000000UL,
This time, using Platform IO toolchain, it works! I checked it with a scope and I am getting 10 MHz as the clock frequency.
Scope screenshot says 9.62 MHz but it is 10 MHz when I change the horizontal scale.
I am pretty sure I am missing something obvious here.
Any ideas on what must be going on?
Sketch:
#include <Arduino.h>
#include <U8g2lib.h>
#include <SPI.h>
#include <Wire.h>
U8G2_SSD1306_128X64_NONAME_F_4W_HW_SPI display1(U8G2_R0, /* CS = */ 16, /* DC = */ 17, /* RS = */ 4);
void setup(void) {
display1.begin();
display1.setFont(SPINZERO); // Font file not shown here
display1.setFontPosCenter();
}
void loop(void) {
static unsigned long thisMicros = 0;
static unsigned long lastMicros = 0;
for (int i = 0; i < 60; i++) {
display1.clearBuffer();
display1.setCursor(64,20);
display1.print("FPS TEST!");
// tpf = Time Per Frame
unsigned long tpf = thisMicros - lastMicros;
display1.setCursor(64,32);
display1.print(tpf);
display1.setCursor(88,32);
display1.print("yS/F");
// fps = Frame Per Second
unsigned long fps;
if (tpf ==0) {
fps = 0;
} else {
fps = 1000000/tpf;
}
display1.setCursor(64,44);
display1.print(fps);
display1.setCursor(88,44);
display1.print("FPS");
display1.sendBuffer();
lastMicros = thisMicros;
thisMicros = micros();
}
}