I'm in the proces of changing the addresses of a few IIC I2C backpacks on some 2 x 16 LCD displays by adding jumpers to pins AO A1 and A2. Before I put iron the to the job, is it a simple jump or do I need a resistor?
Thanks
If you have a PCF8574 chip on the backpack, look at page 3 of the data sheet, pin functions table, top row. (RTFM?)
If you don't have the PCF chip on the breadboard, we would need to know what it is.
groundFungus:
If you have a PCF8574 chip on the backpack, look at page 3 of the data sheet, pin functions table, top row. (RTFM?)If you don't have the PCF chip on the breadboard, we would need to know what it is.
You seem to have misunderstood my question. I have the datasheet for the PCF8574 and understand which pins to bridge to give me a range of specific addresses.
My question was do I need to use resistors or just a simple bridge.
I have several LCD's with the I2C interfaces on them and they all have A0, A1, and A2 tied directly to VCC. Keep that in mind before tying any of those pins to ground.
From the linked data sheet.
Address inputs 0 through 2. Connect directly to VCC or ground. Pullup resistors are not needed.
Have and read are not the same.
The deviceAddress is a 7-bit value, and it is: 0b0100A2A1A0 (range: 0b0100000- 0b0100111)
The last three bits (A2A1A0) are the solder bridges on the IO Extender Board (Fig-1). For my board, the bridges are shown open circuited, and most probably they are terminated to 5V by pull-up resistors which are not shown in the schematic of the IO Extender. If this is the case (can be verified using multi-meter), then one or more of the bridges can be directly shorted to get 0 or be kept open to get 1. Mine I2C LCD is having the deviceAddress ob0100111 = 0x27).
Figure-1: 8574 IO extender based 16x2 LCD