Introduction
Mode: HD702 Introduction : The HD702 LCD is a FriendlyELEC developed LCD with capacitive touch panel. Its resolution is 800 x 1280. Its backlight is adjustable via FriendlyELEC' s one-wire technology. It works with FriendlyELEC' s4412/4418/6818 boards under UbuntuCore+QtE/Debian and Android. Its driver is open source.
The HD702 has a black bezel with mounting holes making it easily deployed in various situations. Note: we have a more detailed introduction to the one-wire technology in the appendix.
I Appendix: One-Wire Technology
As for most ARM boards we observed that using CPU' s ADC conversion did n' t work very well for large-size LCDs (7" and larger) with four-wire resistive touch. Some vendors use an external USB or UART module to connect these LCDs. To save CPU' s hardware resources and minimize usage of external modules we developed the one-wire technology which only uses a single GPIO pin and we have integrated this technology in all our LCD controller boards. This technology uses an MCU to communicate with the touch panel' s chip (we use the ADS7843 chip or other chips compatible with ADS7843) and process the four-wire resistor' s analog signals and output the filtered stable signals to the ARM board via GPIO. We tested this technology in various LCDs and it worked very well even for a large LCD of 19" and some commonly observed issues such as screen flipping and jittering were not encountered. Today most LCDs whose size is less than 12" have LED backlight. We use the one-wire' s MCU to process the backlight as well. The backlight is set with a range of values. Users can set a value to the backlight and this value is passed to MCU for processing via one-wire' s GPIO pin. Each Friend IyARM' s LCD module has a unique ID which is saved in the one-wire' s MCU. When the MCU reads the ID information from GPIO signals it will recognize the LCD model and instruct the bootloader to load the corresponding LCD driver, making a FriendlyARM LCD plug and play. As for the one-wire technology for our LCDs with capacitive touch we removed the resistive touch panel' s chip but kept the backlight adjusting function and LCD' s ID information. Therefore the communication between the capacitive touch and the ARM board is still standard IIC.
Please note that the one-wire technology is different from the commonly known single-bus communication. Actually in the ARM board we use a PWM timer (not PWM pins) to generate the communication frequency (9600Hz). For more details please refer to the driver' s source code.
We have a 30-day return policy, which means you have 30 days after receiving your item to request a return.
To be eligible for a return, your item must be in the same condition that you received it, unworn or unused, with tags, and in its original packaging. You’ll also need the receipt or proof of purchase.
To start a return, you can contact us at alex@friendlyarmtr.com. If your return is accepted, we’ll send you a return shipping label, as well as instructions on how and where to send your package. Items sent back to us without first requesting a return will not be accepted.
You can always contact us for any return question at alex@friendlyarmtr.com.
Damages and issues
Please inspect your order upon reception and contact us immediately if the item is defective, damaged or if you receive the wrong item, so that we can evaluate the issue and make it right.
Exceptions / non-returnable items
Certain types of items cannot be returned, like perishable goods (such as food, flowers, or plants), custom products (such as special orders or personalized items), and personal care goods (such as beauty products). We also do not accept returns for hazardous materials, flammable liquids, or gases. Please get in touch if you have questions or concerns about your specific item.
Unfortunately, we cannot accept returns on sale items or gift cards.
Exchanges
The fastest way to ensure you get what you want is to return the item you have, and once the return is accepted, make a separate purchase for the new item.
Refunds
We will notify you once we’ve received and inspected your return, and let you know if the refund was approved or not. If approved, you’ll be automatically refunded on your original payment method. Please remember it can take some time for your bank or credit card company to process and post the refund too.