Null modem with full handshaking for STM32F3DISCOVERY

[Good B]

Posted on April 28, 2017 at 12:03

Hi,

I would like to control the E3631A power supply by RS232.

I use the null modem without handshaking (RX, TX and GND).

I can set the power supply but when I use *IDN? or SYSTem:ERRor? command.

The power supply didn't respond and no the signal at TX pin of the power supply.

When I use the null modem with full handshaking. I can set and get massage from the power supply.

Could you suggest for me?

Thank you

[S.Ma]

Posted on April 28, 2017 at 13:26

In the manual of the lab equipment we can read equipment specific behaviour respective to DTR/RTS:

DTR/DSR Handshake Protocol The power supply is configured as a DTE (Data Terminal Equipment) device and uses the DTR (Data Terminal Ready) and DSR (Data Set Ready) lines of the RS-232 interface to handshake. The power supply uses the DTR line to send a hold-off signal. The DTR line must be TRUE before the power supply will accept data from the interface. When the power supply sets the DTR line FALSE, the data must cease within 10 characters. To disable the DTR/DSR handshake, do not connect the DTR line and tie the DSR line to logic TRUE. If you disable the DTR/DSR handshake, also select a slower baud rate to ensure that the data is transmitted correctly. The power supply sets the DTR line FALSE in the following cases: 1 When the power supply’s input buffer is full (when approximately 100 characters have been received), it sets the DTR line FALSE (pin 4 on the RS-232 connector). When enough characters have been removed to make space in the input buffer, the power supply sets the DTR line TRUE, unless the second case (see next) prevents this.

extract of page 60 of the

https://courses.engr.illinois.edu/ece437/ref/E3631-90002.pdf

. 

Adjust the MCU setting to match the specifics of the equipment which does not use RTS/DTS only for flow control.

[Good B]

Posted on April 28, 2017 at 14:41

Hi

Thank you very much for your help.

I am sorry. I forgot I use the computer for using the null modem with full handshaking to control the power supply.

But the STM32F3DISCOVERY board has only TX and RX pin.

Could you suggest for me?

Thank you

[Tesla DeLorean]

Posted on April 28, 2017 at 14:46

The STM32F3 also outputs at CMOS levels, not RS232 level, so a converter is required.

The STM32 can provide for CTS/RTS pin as hardware controls to the USART, but could implement them as GPIO along with DTR\DSR, and used by you in *software*. Review the signalling expected by your device.