Need help with mega8 usart......

[Manchested]

Hi all,

I would like to connect a mega8 to a peripheral (modem chip, which uses UART) via usart, but also connect the controller to a PC via the same pins. I wonder if this will cause any problem?

 

[bigdogguru]

I would like to connect a mega8 to a peripheral (modem chip, which uses UART) via usart, but also connect the controller to a PC via the same pins. I wonder if this will cause any problem?

Caution. Yes, it could easily damage the AVR.

The ATMEGA8 UART TX/RX pins cannot be connected directly to a RS-232 Port of a PC.

A RS-232 Transceiver or Level Shifter, like the MAX232 is required.

I'm not quite sure what you are referring to as a modem chip, please elaborate.

BigDog

 

[Manchested]

Thanks for the info BigDog


Here is the chip I am talking about.

It has to be coupled to a UART Port on the controller.

 

[Manchested]

Does it need an analog switch to switch between two receivers?

 

[bigdogguru]

I looked over the SIG60 Datasheet.

I would have liked to reviewed some appnotes for the SIG60, however there does not appear to be any available on the website.



What other devices will be using the SIG60 for communication besides the ATMEGA8?

The preferred solution would be to utilize a separate SIG60 with RS-232 transceiver for your PC to act as a Master and enable the PC to communication directly with the other SiG60 enabled units on the Power Bus.

Does it need an analog switch to switch between two receivers?

The whole point of using a SIG60 type device is to allow communications over a Power Bus rather than direct serial communications.

What is your overall design plan? What other devices will be enabled with the SIG60?


BigDog

 

[Manchested]

The preferred solution would be to utilize a separate SIG60 with RS-232 transceiver for your PC to act as a Master and enable the PC to communication directly with the other SiG60 enabled units on the Power Bus.

Do you mean the powerline chip can be directly connected to PC using the RS-232 transceiver? Will I still be able to control the alarm by doing that?

I would like to control some alarms through the DC power line which carry the data information as well as 24V DC power.
My plan is to have the following:
On the master side there is:
1. A microcontroller (an atmel controller preferred), interface between the pc & powerline chip
2. PC, which enables selection of the alarms to turn on
3. A powerline chip (came across the SIG60)
4. Data and power seperation circuit

On the slave side:
1. Data and power seperation circuit
2. The same kind of powerline comm chip as on the master side
3. The same kind of mcu as on the master side
4. Alarms driver
5. 5-6 Alarms (buzzers)

for your reference, I have also uploaded a module manual.

 

[Manchested]

anyone could help me out there???

 

[bigdogguru]

Do you mean the powerline chip can be directly connected to PC using the RS-232 transceiver? Will I still be able to control the alarm by doing that?

Yes, the datasheet and the previously attached picture indicate this is possible. Also the SIG60 development board mentions the capability of interfacing the unit with a PC serial port.

Reference: SIG60 Module Manual, Section: 2 .1. Block Diagram Description, pg 3

2 .1. Block Diagram Description

The Module contains all the required hardware for device operation such as a line protection network,
ceramic filters, and a power supply. The board performs an asynchronous UART protocol over DC
power lines at data rates of up to 57.6Kbps. Operation at 115.2Kbps requires dedicated filters. The
SIG60 may also be used as a new physical layer to the LIN protocol. The Module can be connected
directly to a host (Micro controller with UART port or a PC) through its JP1 I/O connector. The EVB
block diagram is described in Figure 2.1

The received data signal from the DC line passes through a protection network into the RxIn input pin
to an Rx amplifier. The amplified signal passes via F0B or F1B pins to an external ceramic filter and
back into RxP input. The SIG60 decodes the data and output it to HDO pin as an asynchronous bit
stream.

On the transmitter side, the host sends UART data to the SIG60 via HDI pin. The asynchronous data is
protected against errors and modulated inside the SIG60. The DTXO pin outputs the digitally
modulated signal to the ceramic filter for shaping. The shaped signal enters the SIG60 via F0B or F1B
pins into an output amplifier. The modulated data on TxO pin drives the DC line via the protection
network. To connect HDI and HDO signals to a PC, additional RS232 or USB interface is required.

The SIG60 is a 3.3v device, therefore the HDI/HDO lines would require an appropriate 3.3v RS-232 transciever for the PC serial port or a USB to Serial Bridge Device like the FTDI FT232 for a PC USB interface.

I would like to control some alarms through the DC power line which carry the data information as well as 24V DC power.
My plan is to have the following:
On the master side there is:
1. A microcontroller (an atmel controller preferred), interface between the pc & powerline chip
2. PC, which enables selection of the alarms to turn on
3. A powerline chip (came across the SIG60)
4. Data and power seperation circuit

On the slave side:
1. Data and power seperation circuit
2. The same kind of powerline comm chip as on the master side
3. The same kind of mcu as on the master side
4. Alarms driver
5. 5-6 Alarms (buzzers)

for your reference, I have also uploaded a module manual.

Your plan sounds reasonable, however the PC would most likely be the master with the ATMEGA8 acting as a slave system controller.

BigDog