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The Master Interface Module allows users to interface I2C slave cards to a PC using one of three interfaces, RS232, USB or optional Ethernet. The Module has a high speed 400kHz I²C bus, 23-channels of bidirectional digital I/O and on-board 256KBit EEPROM.
Key Features
- Multiple Interfaces (RS232, USB, Optional Ethernet)
- One Interface Controls All Desired Slave Boards
- Wide Voltage Input
- Robust, Flexible Design
- Multiple Connection Methods (Piggyback, Ribbon)
- Low Cost
- Small Size
- Multiple Driver Downloads (LabView, Python, .NET)
- All Components Fully Traceable
Two different build options are available to reduce cost to users.
Master Interface-ETH, Master Interface Module fully populated with all 3 interfaces.
Master Interface, Master Interface Module without Ethernet interface.
Specifications
Connectivity
I2C Bus
The Master Interface Module comes with a master I²C bus for all slave board communications and is also available on CN3 for connection to any other device with a slave I²C interface. As supplied the I²C interface is set in standard mode (100kHz), this can be changed to Fast Mode (400kHz) by sending the commands shown in the communications section.
The Module is fitted with a device that controls all I²C bus specific sequences, protocol, arbitration and timing so control sequences to the Module become very simple.
I2C Bus Timing
Communications
All communications to the Master Interface Module and Slave Modules are made by sending string commands to COM ports or virtual COM ports. No drivers are required for the RS232 interface, just simply send and receive data to the COM port the Module is connected to. The USB and Ethernet interface require drivers to function, once the drivers are installed the device will appear as a virtual COM port and data can be sent to and from the Module. It is also possible to send data over Ethernet using TCP. The Ethernet device server IP address can also be changed along with many other settings by installing the Lantronix device installer.
USB Drivers
http://www.ftdichip.com/Drivers/VCP.htm
Ethernet Drivers
http://www.lantronix.com/products/com-port-redirector/
http://www.lantronix.com/products/deviceinstaller/
Commands
1.0.0 – Send data over I²C Bus
To send data to a slave I²C device the following commands need to be sent:
| The 1st byte (01010011, 0x53, S) | Start the I2C bus |
| The 2nd byte (???????0, ?, ?) | Address the I²C slave device plus 0 (first 7 bits = slave address, last bit (0) = write) |
| The 3rd byte (????????, ?, ?) | Number of data bytes to send (between 1 and 256 bytes) |
| Data Bytes | Send data bytes |
| Last byte (01010000, 0x50, P) | Stop the I2C bus |
1.1.0 – Read data over I²C Bus
To read data to a slave I²C device the following commands need to be sent:
| The 1st byte (01010011, 0x53, S) | Start the I2C bus |
| The 2nd byte (???????1, ?, ?) | Address the I²C slave device plus 1 (first 7 bits = slave address, last bit (1) = read) |
| The 3rd byte (????????, ?, ?) | Number of data bytes to read (between 1 and 256 bytes) |
| The 4rd byte (01010000, 0x50, P) | Stop the I2C bus |
*After this command you must read the number of data bytes from the seral bus.
2.0.0 - Using Master Module GPIO Ports 0 and 1 as Outputs
First configure the digital pins to be outputs:
Binary = 01010011-01001110-00000010-00000110-00000000-01010000
Hex = 0x53-0x4E-0x02-0x06-0x00-0x50
ASCII = S-N-STX-ACK-NUL-P
| The 1st byte (01010011, 0x53, S) | Start the I2C bus |
| The 2nd byte (01001110, 0x4E, N) | Address the GPIO function |
| The 3rd byte (00000010, 0x02, STX) | We need to send 2 bytes of data. (4th & 5 th byte) |
| The 4th byte (00000110, 0x06, ACK) | Address Port 0 I/O direction register |
| The 5th byte (00000000, 0x00, NUL) | Set all pins to be outputs |
| The 6th byte (01010000, 0x50, P) | Stop the I2C bus |
This has set port 0 to be outputs. The same command is required to set port 1 to outputs but the 4th byte will need to be 00000111 (0x07(BEL)) to address Port 1 IO direction register.
We can now write to the GPIO 0 & GPIO 1 registers to change the state of the IO pins.
Binary = 01010011-01001110-00000010-00000001-????????-01010000
Hex = 0x53-0x4E-0x02-0x01-0x??-0x50
ASCII = S-N-STX-SOH-?-P
| The 1st byte (01010011, 0x53, S) | Start the I2C bus |
| The 2nd byte (01001110, 0x4E, N) | Address the GPIO function |
| The 3rd byte (00000010, 0x02, STX) | We need to send 2 bytes of data. (4th & 5 th byte) |
| The 4th byte (00000000, 0x00, NUL) | Address Port 0 register |
| The 5th byte (?) | Set the state of Port 0, LSB=P0.0, MSB=P0.7, 0=LOW, 1=HIGH |
| The 6th byte (01010000, 0x50, P) | Stop the I2C bus |
The same command is required to change the state of port 1 but the 4th byte will need to be 00000001 (0x01(SOH)) to address the GPIO 1 register.
2.1.0 - Reading the Master Module GPIO Ports 0 and 1 State
Binary = 01010011-01001110-00000001-00000000-01010000-01010011-01001111-00000001-01010000
Hex = 0x53-0x4E-0x01-0x00-0x50-0x53-0x4F-0x01-0x50
ASCII = S-N-SOH-NUL-P-S-O-SOH-P
| The 1st byte (01010011, 0x53, S) | Start the I2C bus |
| The 2nd byte (01001110, 0x4E, N) | Address the GPIO function |
| The 3rd byte (00000001, 0x01, SOH) | Send 1 byte of data. (4th byte) |
| The 4th byte (00000010, 0x00, NUL) | Address Port 0 register |
| The 5th byte (01010000, 0x50, P) | Stop the I2C bus |
| The 6th byte (01010011, 0x53, S) | Start the I2C bus |
| The 7th byte (01001111, 0x4F, O) | Address the GPIO function asking to send data |
| The 8th byte (00000001, 0x01, SOH) | Send 1 byte of data |
| The 9th byte (01010000, 0x50, P) | Stop the I2C bus |
*After this command you must read 1 byte of data from the seral bus. This byte of data will show the state of the port, LSB=P0.0, MSB=P0.7, 0=LOW, 1=HIGH.
The same command is required to read the state of port 1 but the 4th byte will need to be 00000001 (0x01(SOH)) to address the GPIO 1 register.
2.2.0 - Using Master Module GPIO Ports 0 and 1 as Inputs
First configure the digital pins to be inputs:
Binary = 01010011-01001110-00000010-00000110-11111111-01010000
Hex = 0x53-0x4E-0x02-0x06-0xFF-0x50
ASCII = S-N-STX-ACK-ÿ-P
| The 1st byte (01010011, 0x53, S) | Start the I2C bus |
| The 2nd byte (01001110, 0x4E, N) | Address the GPIO function |
| The 3rd byte (00000010, 0x02, STX) | We need to send 2 bytes of data. (4th & 5th byte) |
| The 4th byte (00000110, 0x06, ACK) | Address Port 0 I/O direction register |
| The 5th byte (11111111, 0xFF, ÿ) | Set all pins to be inputs |
| The 6th byte (01010000, 0x50, P) | Stop the I2C bus |
This has set port 0 to be inputs. The same command is required to set port 1 to inputs but the 4th byte will need to be 00000111 (0x07(BEL)) to address the Port 1 IO direction register.
We can now read the state of the input ports as shown in section 1.1.0.
3.0.0 - Using Master Module GPIO 0 to 7 as Outputs (on Auxiliary Connector)
First we need to set the GPIO 0 to 7 as outputs.
Binary = 01010111-00000010-10101010-01010000-01010111-00000011-10101010-01010000
Hex = 0x57-0x02-0xAA-0x50-0x57-0x03-0xAA-0x50
ASCII = W-STX-a-P-W-ETX-a-P
| The 1st byte (01010111, 0x57, W) | Address the GPIO 0-7 function |
| The 2nd byte (00000010, 0x02. STX) | Select GPIO 0 to 3 |
| The 3rd byte (10101010, 0xAA, a) | Set GPIO0-3 as push-pull outputs |
| The 4th byte (01010000, 0x50, P) | Terminate this frame |
| The 5th byte (01010111, 0x57, W) | Address the GPIO 0-7 function |
| The 6th byte (00000011, 0x03, ETX) | Select GPIO 4 to 7 |
| The 7th byte (10101010, 0xAA, a) | Set GPIO4-7 as push-pull outputs |
| The 8th byte (01010000, 0x50, P) | Terminate this frame |
We can now write to the GPIO 0 to7 register to change the state of the IO pins.
Binary = 01001111-????????-01010000
Hex = 0x4F-0x??-0x50
ASCII = O-?-P
| The 1st byte (01001111, 0x4F, O) | Address the GPIO 0-7 register |
| The 2nd byte (?) | Set the state of GPIO 0-7, LSB=GPIO 0, MSB=GPIO 7, 0=LOW, 1=HIGH |
| The 3rd byte (01010000, 0x50, P) | Terminate this frame |
3.1.0 - Reading the Master Module GPIO Port 2 State
Binary = 01001001-01010000
Hex = 0x49-0x50
ASCII = I-P
| The 1st byte (0101001, 0x49, I) | Ask for status of GPIO 0-7 |
| The 2nd byte (01010000, 0x50, P) | Terminate this frame |
*After this command you must read 1 byte of data from the seral bus. This byte of data will show the state of the port, LSB=P0.0, MSB=P0.7, 0=LOW, 1=HIGH.
3.2.0 - Using Master Module GPIO Port 2 as Inputs
First we need to set the GPIO 0 to 7 as inputs.
Binary = 01010111-00000010-01010101-01010000-01010111-00000011-01010101-01010000
Hex = 0x57-0x02-0x55-0x50-0x57-0x03-0x55-0x50
ASCII = W-STX-U-P-W-ETX-U-P
| The 1st byte (01010111, 0x57, W) | Address the GPIO 0-7 function |
| The 2nd byte (00000010, 0x02, STX) | Select GPIO 0 to 3 |
| The 3rd byte (01010101, 0x55, U) | Set GPIO0-3 as inputs |
| The 4th byte (01010000, 0x50, P) | Terminate this frame |
| The 5th byte (01010111, 0x57, W) | Address the GPIO 0-7 function |
| The 6th byte (00000011, 0x03, ETX) | Select GPIO 4 to 7 |
| The 7th byte (01010101, 0x55, U) | Set GPIO4-7 as inputs |
| The 8th byte (01010000, 0x50, P) | Terminate this frame |
We can now read the state of the input ports as shown in section 2.1.0.
4.0.0 – Writing Data to EEPROM
The EEPROM memory has 500 pages with 64 bytes of data on each, as shown below.
4.0.1 – Byte Write
To write bytes of data to the EEPROM the following commands need to be sent:
| The 1st byte (10101110, 0xAE) | Address the EEPROM plus 0 (first 7 bits = slave address, last bit (0) = write) |
| The 2nd byte (????????, ?) | Memory address high byte |
| The 3rd byte (????????, ?) | Memory address low byte |
| Data Bytes | Data |
| Stop |
Example:
0xA0, 0x00, 0x00, Data = Addressing byte 1 of page 1
If more than 64 bytes of data are sent the device will automatically roll over to the next page e.g. If 100 bytes of data are sent to page 1, page 1 will contain the first 64 bytes and page 2 will contain the last 36 bytes.
4.0.2 – Page Write
To write a complete page of data to the EEPROM the following commands need to be sent:
Note: A complete page consists of 64 bytes, if less than 64 bytes are sent, the remaining bytes will be refreshed.
| The 1st byte (10101110, 0xAE) | Address the EEPROM plus 0 (first 7 bits = slave address, last bit (0) = write) |
| The 2nd byte (????????, ?) | Memory address high byte |
| The 3rd byte (????????, ?) | Memory address low byte |
| Data Bytes (64 maximum) | Data |
| Stop |
Example:
0xA0, 0x00, 0x00, Data = Addressing Page 0
0xA0, 0x00, 0x01, Data = Addressing Page 1
0xA0, 0x01, 0xF4, Data = Addressing Page 500
4.1.0 – Reading Data from EEPROM
4.1.1 – Current Address Read
This function can be used to read the next byte from a previous read. E.g. if page 1 byte 3 was the last byte read from the device the following command will read page 1 byte 4. After this the address is internally incremented by 1 so if the command is sent again it will read from the next byte in sequence.
| The 1st byte (10101110, 0xAE) | Address the EEPROM plus 0 (first 7 bits = slave address, last bit (1) = read) |
| Read Data Byte | Read the data back |
| Stop |
4.1.2 – Random Read
If you need to read data from a random location the following commands must be sent.
First the location address will need to be set:
| The 1st byte (10101110, 0xAE) | Address the EEPROM plus 0 (first 7 bits = slave address, last bit (0) = write) |
| The 2nd byte (????????, ?) | Memory address high byte |
| The 3rd byte (????????, ?) | Memory address low byte |
| Stop |
Then the data can be read by the following command:
| The 4th byte (10101111, 0xAF) | Address the EEPROM plus 0 (first 7 bits = slave address, last bit (1) = read) |
| Read Data Byte | Read the data back |
| Stop |
After a random read command, the internal address counter will point to the address location following the one that was just read.
4.1.3 – Sequential Read
A sequential read allows users to define a start address as a random read does but allows multiple bytes to be read back with a single command by sending acknowledgements between the bytes received.
First the location address will need to be set:
| The 1st byte (10101110, 0xAE) | Address the EEPROM plus 0 (first 7 bits = slave address, last bit (0) = write) |
| The 2nd byte (????????, ?) | Memory address high byte |
| The 3rd byte (????????, ?) | Memory address low byte |
| Stop |
Then the data can be read by the following command:
| The 4th byte (10101111, 0xAF) | Address the EEPROM plus 0 (first 7 bits = slave address, last bit (1) = read) |
| Read Data Byte | Read the data back |
| Acknowledge | |
| Read Data Byte | Read the data back |
| Etc. | |
| Stop |
After each acknowledge, the internal address counter will point to the address location following the one that was just read.
5.0.0 – Connection to Slave Boards
TBC