I2C connection debug for NodeMCU

---
c1
c2
c3
Device found at address 0x68,sda2,scl4
Device found at address 0x76,sda2,scl4
c4
c5
c6
c7

---
[http://nodemcu.a1w.ca/post/150677174324/use-an-i2c-scanner]
-- This code is public domain, attribution to gareth@l0l.org.uk appreciated.

local pins = {1, 2, 4, 5, 6, 7, 8}
local scl, sda = nil

print("Searching for I2C device")

for scl = 1, 7 do
  for sda = 1, 7 do
    tmr.wdclr()
    if sda ~= scl then
      i2c.setup(0, sda, scl, i2c.SLOW)
      for i = 0, 127 do
        i2c.start(0)
        if i2c.address(0, i ,i2c.TRANSMITTER) then
          print("Device found at address 0x" .. string.format("%02X,sda%d,scl%d", i, sda, scl))
          --print("Device is wired: SDA to GPIO" .. pins[sda] .. " - IO index " .. sda)
          --print("Device is wired: SCL to GPIO" .. pins[scl] .. " - IO index " .. scl)
        else
          --
        end
        i2c.stop(0)
        --print(string.format("%02X,a%d,c%d", i, sda, scl))
      end
    end
  end
  print(string.format("c%d",  scl))
end

---

Accelor Sensor:
The slave address of the MPU-9250 is b110100X which is 7 bits long. The LSB bit of the 7 bit address is determined by the logic level on pin AD0. This allows two MPU-9250s to be connected to the same I2C bus.  When used in this configuration, the address of the one of the devices should be b1101000 (pin AD0 is logic low) and the address of the other should be b1101001 (pin AD0 is logic high).

The reset value is 0x00 for all registers other than the registers below.
• Register 107 (0x01) Power Management 1
• Register 117 (0x71) WHO_AM_I

Magnet Sensor:
WIA reg =00H val =48H


BMP280 Sensor:
The 7-bit device address is 111011x. The 6 MSB bits are fixed. The last bit is changeable by SDO value and can be changed during operation. Connecting SDO to GND results in slave address 1110110 (0x76); connection it to VDDIO results in slave address 1110111 (0x77)



----

id  = 0
sda = 2
scl = 4

-- initialize i2c, set pin1 as sda, set pin2 as scl
i2c.setup(id, sda, scl, i2c.SLOW)

-- user defined function: read from reg_addr content of dev_addr
function read_reg(dev_addr, reg_addr)
    i2c.start(id)
    ack=i2c.address(id, dev_addr, i2c.TRANSMITTER)
    i2c.write(id, reg_addr)
    i2c.stop(id)
    i2c.start(id)
    i2c.address(id, dev_addr, i2c.RECEIVER)
    c = i2c.read(id, 1)
    i2c.stop(id)
    return c,ack
end

-- get content of register 0xAA of device 0x77
reg,ack = read_reg(0x68, 0x75)
print(string.format("%02x",string.byte(reg))) --return 0x73 or 0x71
print(ack)
reg,ack = read_reg(0x68, 0x6B)
print(string.format("%02x",string.byte(reg)))  --return 0x01
print(ack)
reg,ack = read_reg(0x76, 0xD0)
print(string.format("%02x",string.byte(reg))) --return 0x58
print(ack)

Serial Port over USB project: STM32F103C8 mini broad + Keil MDK5 IDE - Section 1

Serial Port will be very helpful for visualizing the STM32F103C8 peripherals' sensor outputs. Though it is still ok when sensor provides 1-dimension outputs, it will be very hard for human to watch and understand a vector of ouputs changing with time. For example, the outputs from 9-axis motion sensor, Invensense MPU9250 whose outputs include 3-axis gyroscope, a 3-axis accelerometer and 3-axis compass. And some MPU module also includes air pressure sensor Bosch BMP280.

Serial Port can deliver real-time sensor data to host computer (Windows) which uses Python GUI to visualize sensor data streams. And it is what has been done by Invensense eMD software. However, eMD requires an extra USB to Serial (UART) convert to connect STM32 and host computer. Actually, most STM32 chips support USB device mode. It can act as USB CDC ACM device (Serial over USB). So, we don't need any external USB-to-Serial Converter at all.


Prerequisites:
- Keil MDK5 μVision IDE
- STM32F103C8

Step 1: Start a new project in MDK5

Main Menu-> Project-> New μVision Project.
Choose a blank folder for the new project. Click 'Next'
Then a dialog Select Device for Target 'Target 1'... pop-up. Search '103' and you can find that STM32F103C8 appears in device tree. Click 'Ok'.

Step 2: Manage Run-Time Environment
Expand USB->Device in the left most Column'Software Component'

Opt-in 'Core', set Device number to '1', set Device CDC number to '1'. Then, you may notice a list of warning appears at bottom. It is dependence check, since the final application we have just selected relies on other components, such as RTOS::Keil RTX, CMSIS::Core and CMSIS Driver::USB Device, etc.

Expand 'CMSIS->RTOS' and 'CMSIS Driver->USB Device (API)'
And Opt-in the components as shown in figure below:

Then Click 'OK'.

A empty project with many .c and .h files which is related to selected components will be shown.

Step 3: Configuration Wizard: USB
Use configuration wizard to initialize some system and USB parameters

(3.1) In Project browser, Expand 'Target 1'->USB, and double click 'USBD_Config_0.c' to open it.
(3.2) Open tab 'Configuration Wizard'.

(3.3) Change 'Product ID' and 'Product String' to match the info in STM32 USBD CDC driver. I am not sure whether other ID or String matching is needed or not.

RTE Config
Opt-in USB

Step 4: Configuration Wizard: CMSIS->RTX_Conf_CM.c

Set RTX Kernel Time tick to 72MHz (identical to RTE_device.h Clock configuration->System Clock)

Step 5: Add a new file 'USB Device CDC' via User Code Template.

Add define and function declaration to 'USBD_User_CDC_ACM_0.c'
---

#define  UART_BUFFER_SIZE       128     // UART Buffer Size
static            uint8_t       uart_tx_buf[UART_BUFFER_SIZE];
---

// Called when new data was received from the USB Host.
// \param[in]   len           number of bytes available to read.
void USBD_CDC0_ACM_DataReceived (uint32_t len) {
  int32_t cnt;

  (void)(len);

  //if (ptrUART->GetStatus().tx_busy == 0U) {
    // Start USB -> UART
    cnt = USBD_CDC_ACM_ReadData(0U, uart_tx_buf, UART_BUFFER_SIZE);
    if (cnt > 0) {
      //ptrUART->Send(uart_tx_buf, (uint32_t)(cnt));
USBD_CDC_ACM_WriteData(0U, uart_tx_buf, cnt);
    }
  //}
}
---

Step 6: Add 'main.c' file to 'Source Group 1'
Use User Code Template->CMSIS->RTOS Keil RTX-> CMSIS RTOS 'main' function

Change code to:

---
#include "cmsis_os.h"
#include "rl_usb.h"
---
/*
 * main: initialize and start the system
 */
int main (void) {
  //osKernelInitialize ();                    // initialize CMSIS-RTOS

  // initialize peripherals here
  USBD_Initialize (0U); /* USB Device 0 Initialization */
  USBD_Connect (0U); /* USB Device 0 Connect */
  // create 'thread' functions that start executing,
  // example: tid_name = osThreadCreate (osThread(name), NULL);

  //osKernelStart ();                         // start thread execution
 while (1) {
    osSignalWait (0U, osWaitForever);
  }
}
---

Step 7: Choose 'Menu->Project->Options for Target'
(1) Xtal MHz
My STM32F108C8 uses a 8MHz crystal

(2) Debugger
I uses a very cheap (less than 2 USD) compatible ST-link debugger. In tab 'Debug', choose 'ST-link Debugger'.
Then, click 'Setting' button on the right.

When ST-link is connected to both STM32 mini board and host computer USB, the mini board STM32 chip will be automatically be recognized by MDK5 as show in figure below.

Compiling passes after all these changes. But the work is not yet done. If we just use current object file .axf and load it to STM32 target, USB can't be recognized by host Windows system at all:

It can't get Product ID.

Step 8:

---
//-------- Use Configuration Wizard in Context Menu -----------------

 ---

Uncheck High Speed USB

Step 10: Compile and load to STM32

..