Arduino_Notes - RicoJia/notes GitHub Wiki

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1. CPU, RAM (2k SRAM, DRAM?), IO, ROM

   • DRAM is "dynamic RAM". Reading: when cap is full, it will leak in a few milliseconds.. So set word to on, bit to 1v, if cap is 2v (full), it will flow from cap to bit; else if it's 0v, it will flow the other way. Write: read, empty the cap, then write.

     

   • SRAM is for static RAM, faster, using flip-flops (CMOS), no need to fresh. So faster. Used as cache, because it's big in size, and can't fit as much in a chip as DRAM.

2. Bootloader: software to wait for your program and write to arduino. bootloading is to use an In-System-Programmer (ISP), real hardware

   • Arduino may not have a bootloader on it. So replace it with a new chip
   • get 2k more space.
   • But you can't use USB
   • select port

3. Baudrate: 9600 bits/second in serial. above 76800. then cable needs to be short

4. software reset arduino:

   void (*reset)(void) = 0;    // set this function at address 0
   reset(); 
   // HOWEVER, if you print right before reset, serial print might be corrupted

5. Arduino print number: Serial.print(78, DEC) gives "78"

   • Serial.println(String(execution_time)); print byte
   • WARNING: serial.println will send stuff to serial

6. Problem with delete[]

   • Try not to delete[] arrays, there are certain complications that we don't find answers for yet.

1. Installation in Arduino

   • Choose DOIT DEVKIT v1

2. Modes

   • 活动模式：在这种模式下，Wi-Fi和蓝牙发射器和接收器的所有部分都是活动的。在这种情况下，电流消耗在80和260mA之间。
   • 调制解调器睡眠模式：处理器仍处于活动状态，但Wi-Fi和蓝牙已禁用。在这种情况下，电流消耗在3到20mA之间。
   • 轻度睡眠模式：主处理器停止工作，但RTC单元和ULP处理器单元仍处于活动状态。电流消耗约为0.8 mA。
   • 深度睡眠模式：只有RTC单元处于活动状态。在这种情况下，Wi-Fi和蓝牙通信的数据存储在RTC的存储器中。在此模式下，电流消耗在10到150μA之间。
   • 休眠模式：除了用于时钟的RTC定时器和连接到RTC的一些I / O引脚外，所有单元均被禁用。 RTC定时器或连接的引脚可以将芯片从此状态唤醒。在这种情况下，电流消耗约为2.5μA。

3. About ESP32

   • Datasheet
   • RTC_GPIO is for low-power mode
     • PWM channel generates a PWM.
     • vin is 5v!
   • ~ means PWM.
   • D for dual core. ours is dual core. MIFA antenna, F shaped antenna, high bandwidth per area
   • has internal LED
   • also has IR comm
   • Power: 5-12v external power
   • SPI flash: spi has choose line, but still slow for memory.

4. Communications

   1. HTTP, run post and get, but HTTP is quite tricky
   2. WebSocket: persistent HTTP calls
   3. MQTT, iot protocals, light weight, industry standard

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1. serial comm (tx->rx). Should use <SoftwareSerial.h> since there's one tx, rx, and they clash with the comm
2. default pwd: 1234

1. Sample Schematic:

   

2. Tutorial

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1. ros serial: getting started

   • Note: as indicated here, for groovy and above, installing ros_lib is a one-time thing:

     cd sketch_book/libraries
     rosrun rosserial_arduino make_libraries.py .
     

   • Note: ros and serial (like uploading) will clash

   • generate msgs see here:

     # in ros package
     rosrun rosserial_client make_libraries ~/sketchbook/libraries
     

     • Note: catkin_make doesn't delete the old srv file (just overwrites it). So need to delete build and devel if old srv file was generated

   • How to write service see here

   • run the node rosrun rosserial_python serial_node.py _port:=/dev/ttyUSB0

   • A logic error in arduino will make the rosserial topic drop msg.

2. print float:

   char result[32]; // Buffer big enough for 7-character float
   dtostrf(commanded_angles[i], 6,2, result);
   nh.loginfo(result);

3. Subscribe: array in .msg is tricky. List them out instead

   • when you reach above 90% memory, the arduino will become spooky

4. publish: array, string needs to have length specified first. Also, you have to use ptr for deserialization. link

   joint_msg.commanded_angles_length = 6; 
   joint_msg.commanded_angles = &current_angles[0];
   
   joint_msg_pub.publish(&joint_msg); 
   nh.loginfo("hehe");
   nh.spinOnce();