Microcontroller for driving R61505V round lcd  - Page 1
Forum section: electronics / general

author: Boogami
author_rank: Contributor
timestamp: July 19, 2017, 02:31:03 pm
content: Hello,I am working on a personal project and I have a round lcd like this onehttps://ae01.alicdn.com/kf/HTB1vT.THFXXXXXXaXXXq6xXFXXXB/Free-ship-1-38-inch-Round-TFT-LCD-220x220-30pin-for-Moblie-screen.jpg.I don't know what mcu should i choose for driving this display because it has 8 bit parallel interface and the maximum voltage is 2.9V.The STM32L4 mcus seems to have an lcd controller but that option is on 144 lqfp packages and I want to stay with an easy to solder mcu.I have also attached the datasheet for this display.Thank you.

author: newbrain
author_rank: Super Contributor
timestamp: July 19, 2017, 05:58:05 pm
content: There's no need for a specific LCD interface, as thecontroller chipin this display is hardwired for an 8080-like 8 bit bus.Moreover, the LCD peripheral of the STM32L4 is good for driving classic segment displays, not TFT ones with an integrated controller.You are completely free to choose any MCU that:Can provide enough IOs, either directly or through I2C/SPI port extenders.Can work at the required 2.9VOne MCU peripheral that might come handy is a controller for external memory, which allows you to map the display simply as 2 memory positions (one for commands and one for data), but I don't think it should primarily drive your selection.So, just choose what you are more comfortable with: Atmel, STM32xxxx, PSoC, etc.

author: krho
author_rank: Regular Contributor
timestamp: July 19, 2017, 06:12:00 pm
content: stm32L4 is fine. You need to look at FSMC (flexible static memory controller)

author: Boogami
author_rank: Contributor
timestamp: July 19, 2017, 08:31:51 pm
content: Thank you all for the answers.I've selected STM32L496VET6http://www.farnell.com/datasheets/2283396.pdf?_ga=2.241025347.1384314487.1500375453-365338777.1495706486%27and it has FMC Bank1 available.In the controller chip datasheet it says that I can drive IOVCC and VCC with 3.3v but in the screen datasheet it says 2.8v.Can I use 3.3v from the mcu without using a level shifter? And if I can't do that can someone suggest me a level shifter?

author: krho
author_rank: Regular Contributor
timestamp: July 20, 2017, 05:18:06 am
content: Why do you need level shifter? Just power stm with 2.8 and done.

author: Boogami
author_rank: Contributor
timestamp: July 20, 2017, 06:33:09 am
content: Because I use other parts too. Here is a rough block diagram with the parts that I want to use.

author: JPortici
author_rank: Super Contributor
timestamp: July 20, 2017, 11:18:39 am
content: Quote from: newbrain on July 19, 2017, 05:58:05 pmor a MCU that has a parallel / display interface, whatever they want to call it. ST uses FSMC if i remember righti recommend you READ the device datasheet before settling on the MCU. for example, lower pin count packages usually have only 8 bit data width available and/or no address lines available. Depending on your use case it could be a problem

author: newbrain
author_rank: Super Contributor
timestamp: July 20, 2017, 12:05:29 pm
content: Quote from: Boogami on July 20, 2017, 06:33:09 amIf you can't run the whole system at 2.8V, you might check whether it's possible to just run the MCU and display at that voltage (possible problems: noise immunity and High logic level, need for >Vcc tolerant IOs).Yet another possibility might be to configure the MCU pins as Open Drain, and use pull ups (but check the timing).If none of the above applies, there are several level translators that can be used, e.g. TITXS0108Eand the 4 bit version (that would cover the full display interface). They are not especially chip, though.Quote from: JPortici on July 20, 2017, 11:18:39 amYes, FMC/FSMC for STM32s, EMIF component for PSoCs.Still, even bit-banging the transaction would amount to 5-6 lines of C code as only 8 data bits, 3 control lines (WE,OE,CS) and one address line (command/data) are needed.If the OP is familiar with a specific brand/family, the effort of learning a new set of peripherals/library or even a new toolchain or IDE may very well be much larger than the coding and testing of a couple of simple functions, and the trade-off in efficiency should be tolerable; that was the reason of my advice.

author: JPortici
author_rank: Super Contributor
timestamp: July 20, 2017, 03:07:48 pm
content: good thing about parallel port drivers / memory controllers is that DMA can do all the thing while you actually do something with the MCU(or i can use an XMOS with a core solely for the memory interface)

author: krho
author_rank: Regular Contributor
timestamp: July 20, 2017, 05:48:48 pm
content: Also why adding another chip ontoto the board e.g UART to USB. You have the USB inside a chip, and STM provides CDC code..

author: Boogami
author_rank: Contributor
timestamp: July 20, 2017, 06:53:01 pm
content: Quote from: newbrain on July 20, 2017, 12:05:29 pmI am familiar with stm32f4 and that is why I wanted to go with something from them.Quote from: JPortici on July 20, 2017, 03:07:48 pmI haven't used an XMOS chip before. How hard it is to work with?Quote from: krho on July 20, 2017, 05:48:48 pmI thought that it was a good idea to use a dedicated chip for the USB task.And also thanks for all the help.

author: JPortici
author_rank: Super Contributor
timestamp: July 20, 2017, 07:20:48 pm
content: Quote from: Boogami on July 20, 2017, 06:53:01 pmnevermind, it's kind of an inside jokeIMHO: if you have a chip with FSMC (for ST, other name, same thing, for others) you just have to set it up properly and update the framebuffer in RAM if you need to change the displayed image, the peripheral will do all of the hard work.then, if you have USB on board and have the available cycles, i would use it instead of an external chip. external chip costs a lot in terms of money and board space (well, a pic16f1455, programmed as an USB-UART bridge or something will be as small as a 3x3mm QFN, no need for crystals) and you are limited by them in what transfert speed you can achieve.