At Vop=0xBF, my unit was initializing electronically, but had a blank display (or solid-black, I can't remember now.) Anyway, I had to play with this value, and 0xB3 ended up working for me, so if you are initializing to this sequence and having trouble, try varying this parameter. I found my display to be somewhat sensitive to this value. It is 0x80, or'ed together with a 7-bit Vop value. (2) The second command byte (the 0圎0 shown above) is not arbitrary. (1) I confirm this intialization sequence works, with the clarification noted in #2 below. This wasn't totally clear to me from reading the datasheet. The Vout pin: Looks like you don't have to worry about it on this product, but the bare LCD will generate positive 6-9V on that pin. Interestingly, the display also seems to work fine with a floating Vdd pin - it must draw sufficient power just from i/o via clamping diodes not surprising when you consider how low-power it is. If the bus is shared, frame the entire transaction, not every individual byte you send to the LCD. This means that if it's the only device on the SPI bus, don't bother framing the i/o with a chip-select pin. The LCD will work with the chip-select pin (SCE) tied to ground.
What I found to be the best is to set SCE low and reset high at system bootup, wait 5ms for voltages to stabilize, lower reset, delay by ~1uS (1 nop 8MHz will do), raise reset then send it the initialization sequence above. Reset/initialization can be picky - the datasheet says that the delay from power-up to reset mustn't exceed 30ms. Here it is, in case you were, like me, frustrated over and over again with varying sequences that others claimed to work but they didn't for you:Ġ圎0, //set value of Vop (controls contrast) = 0x80 | 0圆0 (arbitrary)Ġx0C, //enable normal display (dark on light), horizontal addressing It can be driven at 2MHz at these speeds in fact, the LCD will work at even lower voltages but the contrast fades quickly and your microcontroller will likely approach its lower voltage limit too. Yes, it has a board-to-glass connector that ranges from bad to abysmal, but it offers such a simple interface and so many pixels for so little money (obviously less if you buy only the panel.) Here are some clever things I've discovered: This LCD (I have the old-old kind) is absolutely my favorite. Ioctl(fd_spi_dev, SPI_IOC_MESSAGE(1), &tr) * I am expecting to see all segments lit here */ Lcd_write_cmd(0x09) // LCD all segments on Lcd_write_cmd(0x20) // LCD basic commands
Lcd_write_cmd(0x14) // set biad mode 1:40 Lcd_write_cmd(0x04) // set temp coefficient Lcd_write_cmd(0xB8) // set LCD Vop (contrast) Lcd_write_cmd(0x21) // LCD extended commands Ioctl(fd_spi_dev, SPI_IOC_RD_BITS_PER_WORD, &bits) Ioctl(fd_spi_dev, SPI_IOC_WR_BITS_PER_WORD, &bits) Ioctl(fd_spi_dev, SPI_IOC_WR_LSB_FIRST, &lsbsetting) Ioctl(fd_spi_dev, SPI_IOC_WR_MAX_SPEED_HZ, &speed) Ioctl(fd_spi_dev, SPI_IOC_RD_MAX_SPEED_HZ, &speed) Ioctl(fd_spi_dev, SPI_IOC_RD_MODE, &mode) Ioctl(fd_spi_dev, SPI_IOC_WR_MODE, &mode) Here's how I am initializing the LCD: fd_spi_dev = open(device, O_RDWR) Logic says that the pythonĬode must be initializing something that I am missing in my code.
#Squeed cell carrier finder code#
I have a strange issue, when I run this python code first and then my C code, the code works perfect!īut if I run my C code before the python code, I get no output. I successfully installed and ran Adafruit's python-library: I am trying to connect Nokia 5110 LCD to BeagleBone Black Rev-C over SPI protocol using Linux kernel's SPI driver.
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