Interfacing an LCD Module to EVM5535

SRINIVAS KRISHNAGIRI

Hi ti expert,

I want to interface a JHD162A (uses HD44780 controller) LCD module to the EVM5535. I am intending to do this through P2 Expansion Connector. (Initially I got the Samtec connector MEC1-120-02-SDA as per Spectrum Documentation and found mismatch with P2. But now, I have MEC1-130-02-SDA).

First I have an issue of different voltage levels: My JHD162A operates on 5V, and P2 signals are 3.3V. I am planning to use 74lvc4245 to level shift signals between EVM and LCD module. But my most important concern is that the EVM uses LCD_D(5)/GPIO15 to control the UART buffer (Sheet 3 of schematic), even if UART is disabled through the 2-SW3 DIP switch. I understand that the USB to UART is VCP on Channel B (FTDI chip). Channel A is used by CCS4, for emulation (JTAG). My question is whether Channel B is also required by the CCS4 environment.

over 12 years ago

0 SRINIVAS KRISHNAGIRI over 12 years ago

Prodigy 70 points

Hi,

Are there no takers for my question?

thanks

0 Steve Tsang over 12 years ago in reply to SRINIVAS KRISHNAGIRI

TI__Mastermind 23785 points

Only the J2 connector is for CCS. The J1 connector is not.

Regards.

0 Mark M over 12 years ago

TI__Mastermind 30120 points

Hi Srinivas,

Channel B (FTDI VCP) is not required by CCS. Channel B is used to communicate to the virtual com port of a PC via UART (i.e. HyperTerminal).

GPIO15 will override the SW3 DIP setting since GPIO15 is directly connected to the U5 UART buffer input.

When GPIO15 is toggled, the UART signals will be connected to the FTDI Channel B (VCP) through the U5 UART buffer.

Affected UART signals:
LCD_D[12]/UART_RTS/GP[28]/I2S3_CLK
LCD_D[13]/UART_CTS/GP[29]/I2S3_FS
LCD_D[14]/UART_RXD/GP[30]/I2S3_RX
LCD_D[15]/UART_TXD/GP[31]/I2S3_DX

GPIO15 also sinks current from the yellow LED when "low".

You can program your FTDI device to ensure it does not enumerate Channel B as a VCP: www.ftdichip.com/Support/Utilities.htm#FT_Prog

If you have signal corruption, you can remove series resistors between the U5 UART buffer and FTDI: R35, R32, R30, R27.

Or you could remove U5 if you determine it is causing any issue.

The level shifter plan is correct - both 5V and 3.3V are provided on the P2 edge connector. Keep in mind 74lvc4245 has a direction pin which level shifts from A to B or B to A depending on DIR pin.

Hope this helps,
Mark

0 SRINIVAS KRISHNAGIRI over 12 years ago in reply to Mark M

Prodigy 70 points

Hi Mark,

Thanks for your response. Thanks again for your time and effort on this posting.

First, I am happy to note that Channel B is not used by CCS.

I liked your idea of reprogramming the FTDI chip.
I want no or minimal change in the EVM hardware.
Even though I am aware of the eeprom to configure FTDI chip,
I didn’t realise this option until I saw your reply.

Thanks a lot again. I will look into what options I can consider for channel B of FTDI.

In mean time, I modified the led test example provided with the EVM. In the led_test.c file,

I filled in a fixed value of 2 to toggle only GPIO15:

if ( EZDSP5535_LED_on( 2 ) ) .......;

and then reduced the delay also to very low value 1 usec.

This would toggle the GPIO15 at a faster rate to simulate a data bus type of signal.

Then I used a terminal window to see if the FTDI driver is throwing any data on to the terminal.

There is a lot of junk value that is displayed.

This is what can be expected when EBSR Mode bits are changed for the

LCD Module interface to get the LCD interface signals on P2.

If at all any hardware change I intend to do, I will remove the yellow LED to reduce

switching current on VCC_3V3.

Now I have two options for my LCD interface:

To let it be as it is and have a hyper terminal to receive any junk values to 
clear the FTDI driver buffers.
OR
Reprogram FTDI chip configuration.

Thanks again,

Srinivas

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Interfacing an LCD Module to EVM5535