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CFA735 in a bare bones form?


New member
Hi There,

Ive been browsing through your catalog looking for an LCD for a hobby project I am designing.

The project I want to build in simple terms is based around the microchip PIC16F series, and is a small handset style device that will be used to communicate with a Engine Computer. The idea is to query the computer for engine data (tempreture's, RPM and so on) and display mostly ASCII information on an LCD, but also Graph's, have audible alerts that can be user preset, LED's for both status & alerts, and finally have USART comm's to a PC so a PC can also query the engine computer by going via the Handset unit. I also have possibly plans to input additional analog sensors into the device in the future.

So I was here looking for a suitable minimum 4 line graphic LCD to begin prototyping with when I can across the CFA735. It was most interesting to me because it contained a small keypad as well as 4 LED's straight off the bat. Wonderful. The more I read into the unit however the more I realised it was designed to be implemented into a server/computer monitoring device.

So my question is, can the CFA735 come in a "bare bones" form? That is, LCD + Driver, Keypad & LED's? I would interface the PIC16F directly to those devices and use the CFA735 simply as a HID & Display.

OR can I modify the CFA735 extensively enough and utilize the ARM chip? I really like the sound of that, but I am unsure if H1 is the only I/O with the chip (I would need direct port access to communicate with the Engine computer, which simply streams HEX values for the requested parameter), and I would need to be able to modify the boot-loader (use my own preferably, enable encryption & design software for field upgrading) and also provide GPIO to switch transistors at user-preset values for functions such as sound an external buzzer at preset engine temp...

I know this application is left of field for what the CFA735 was designed for, if you think the above options are not practical then could you confirm exactly which LCD is used in the CFA735? I do like it, and I think its the CFAG19264D-TFH-VN but I am not sure.

If you need me to clarify anything please ask.

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CF Tech

The CFA-735 would likely be "perfect" for your project.

The ST Micro STM32 processor ( STM32F103RCT6 ) is way powerful and capable. There are CAN capable pins brought out to H1, as well as SPI, I2C and UART capable pins. You get a USB connector to talk to your laptop, and there is an SD card . . . so you could log the engine parameters effectively forever (with a 32GB uSD).

> can I modify the CFA735 extensively enough and utilize the ARM chip?

No modification should be needed at all. If you need more pins than are available on H1, it is possible to bring out nearly every pin on J_EXP.

Here is a file that shows the map between the processor and H1/J_EXP:

We have an introduction to the starter software for the ST Micro STM32 processor posted here:

The actual code is here:

All you would need besides a CFA-735 would be one of these debuggers:

The PIC is cool and all, but the power, flash and RAM in the STM32, combined with the OPEN code and tools of the ARM makes for a solution that is pretty nice.


New member
Thanks very much for the response!!
Exactly what I wanted to hear, Im only a hobbyist and so far have only develop on the Microchip PIC series IC's so I did want to use one for familiarities sake but I did read up on the ARM chip (72 Mhz clock speed... kinda craps on my 4MHZ PIC16F!!) so looks like I will order a couple of these units and begin testing. I would still need to adapt a daughterboard for GPIO purposes and also cause I need to supply a clock speed back to the engine computer etc... This should be a good starting point though.


CF Tech

What vehicle are you working on? I have a 1946 Chevy truck:
which has a "crash box" transmission. It takes quite a deft touch to shift noiselessly. For ages I have thought of using a CFA-635 (now thinking of a CFA-735) to make a "sync" bar graph. There would be a speed sensor in front of the transmission and one behind it. If the speed difference matches a gear ratio, the bar would read 0 for that gear. If I was really fancy I'd have it drive a stepper motor connected

What is the clock like that you need to supply to the engine computer? Have you thought of trying to do it under firmware (perhaps in a hardware timer's ISR)?

If you need a daughter PCB, here is a typical through-hole mating connector:

And the SMT version:

If you can do it with a harness, in the data sheet:

There is a list of parts to make a mating cable:

The following parts may be used to make a mating cable for J2:
 16-position housing: Hirose DF11-16DS-2C / Digi-Key H2025-ND.
 Pre-terminated interconnect wire: Hirose / Digi-Key H3BBT-10112-B4-ND (typical).

You can go to this page: http://dkc3.digikey.com/PDF/US2011/P0117.pdf and understand to how to make a part number any length and any color terminations for the housing, just start with the number above.


New member
Im working with the Nissan engine's, mainly japanese imports that run the "Consult" protocol from factory. These could be found in most cars from 1990 to around 2000 when OBD-II took over. Interesting idea on the shift indicator you have there, I always enjoy hearing ideas like that.

The engine computer needs to be supplied a 153.6khz clock to begin data comms, I was just going to look for a quartz crystal to do this job running off a daughter board (seemed the most simple), and I also need to bring the RX and TX lines from the ECU and terminate them somewhere too. The RX line streams hex values for the requested engine parameter when you send the corresponding command via TX, and only stops streaming when sent a stop command. You can also do additional things like download engine computer ROM.

Thanks for all the helpful links, I will need to interface H1, but also I think I will need to interface J_EXP also to get 2 pins off the STM32 for input/output to the daughter then to the RX/TX lines. Do you know of any connectors I could use for this?

EDIT: I ordered one of the olimex JTAG debuggers as recommended, and Ive been researching a suitable IDE (Editor, compiler, debug tools & examples if possible) to suit the STM32, preferably open source or free, and have landed on the Eclipse editor with OpenOCD debug, and perhaps the Sourcery GCC... I know this is a little left of field for this forum but do you have a better suggestion?
IDE is one of the reasons I like Microchip :)

Last edited:

CF Support

In our readme, we recommend Sorcery GCC.
Recommended compiler

Sourcery G++ Lite 2011.03-42 for ARM EABI from Mentor Graphics
Eclipse and OpenOCD should work just fine for your needs. We detail a bit about using OpenOCD in our documentation.


New member
Thanks for that response, I have received my 2 CFA735's which I will be using to prototype, so far very impressed with the hardware.

I have 2 final questions; do you have any recommendations for interfacing the expansion port on the CFA735? Im thinking some kind of connector I can solder on, I will need to interface several of the STM32 pins onto a daughterboard, so I can have additional LED's, a Buzzer and to have an interface for the Engine Computer to connect via.

And what is the part number for the LCD on the CFA735? I want to get the datasheet for it & look at pricing, and depending on how successful I am with the STM32 I may not end up using a CFA735 (im rather fond of Microchip & ICSP, and its alot to wrap my head around this new IDE as well as JTAG), but I love the LCD!



New member
Found the connector to interface the expansion pad, SAMTEC FSI-125-03-G-D-AD.

Shame its all SMT tho, going to make prototyping interesting with my shaky hands... might have to lay off the caffeine for a few days first!


CF Tech

We have thought about building a little break-out board to allow easy access to that connector. Have not got to that project yet though :(

Please note that many of the signals on that connector are used other places on the module (LCD interface, for instance) so some care must be taken if you want to use them for another purpose.