User manual

GHI Electronics,LLC Embedded Master User Manual
Hardware and Software Library
Reference
Microsoft.SPOT.Hardware.I2CDevice
11.5. UART
One of the oldest and most common protocols is UART (or USART). TX is the serial data
transmitted and RX is the data received. UART is actually what is used on serial (COM)
ports on computers. The difference between UART on Embedded Master and a serial port
on a PC is that Embedded Master’s UART pins have 3.3V TTL levels where the PC uses
RS232 levels. For proper communication, an RS232 level converter is required. One of the
most common converters is MAX232. If UART is connected between 2 TTL circuits, no
level converter is needed but they should be connected as a null modem. Null modem
means RX on one circuit is connected to TX on the other circuit, and vice versa.
When 2 nodes want to communicate over UART, a predefined baud rate should be used
on both sides. Baud rate is how many bits per second are transferred on the bus.
Embedded Master Module hardware supports 4 COM ports, however, the user is able to
have many more COM ports using USB serial chipsets. For example, there are many USB
<--> Serial cables available and these can be connected directly to Embedded Master.
Check Supported Devices Section.
Maximum Baudrate supported by .Net Micro Framework is 115200. However, any
baudrate can be set using the processor registers directly (GHIElectronics.Hardware.Register).
The maximum baudrate is 9 Mhz. An example is provided later in this section.
PIN# TFT# Name Description
5 5 UART_RXD0 UART 0 (COM1) data receive input
6 6 UART_TXD0 UART 0 (COM1) data transmit output
45 55 UART_RXD1 UART 1 (COM2) data receive pin
50 60 UART_TXD1 UART 1 (COM2) transmit data output
44 54 UART_RTS1 UART 1 (COM2) RTS hardware
handshaking
47 57 UART_CTS1 UART 1 (COM2) CTS hardware
handshaking
41 51 UART_RXD2 UART 2 (COM3) receive data input
42 52 UART_TXD2 UART 2 (COM3) transmit data output
10 10 UART_RXD3 UART 3 (COM4) data receive input
9 9 UART_TXD3 UART 3 (COM4) data transmit output
The following COM ports are available:
Rev. 2.06 TFT Page 64 of 102 www.ghielectronics.com