The HX711 is a commonly available instrumentation amplifier and A-D converter, which lots of vendors sell:
https://www.sparkfun.com/products/13879
I'm playing with some load cells and I got a few HX711's to interface them to an Arduino and a computer. The HX711 actually has 2 channels, A and B, and there's a procedure to switch between them, but at first I thought it didn't work. Then I found that I can switch channels, but every time I do, the device slows way down--the cycle after making a channel change, there's a delay of about 60msec, so if you alternate the channels, you get a full cycle in about 120msec or roughly 8 per second. I'm wondering if I've done this right, or if there's a better procedure to make it faster.
The HX711 has its own oddball serial interface. There's a data line and a clock line, and the device does conversions repeatedly, and sends the data line low when it completes a conversion. A processor has to watch for the lowgoing edge, then send clock pulses which clock out 24 bits of actual data. You can send 1, 2 or 3 extra clock pulses, which make selections for the next cycle--channel A at a gain of 64 or 128, or channel B at a gain of 32. It's those initial lowgoing edges that seem to get slowed down by changing channels. If you don't change channels, it runs at 80 cycles per second. (Or 10, using a selection pin, but I'm trying to use 80.)
https://www.sparkfun.com/products/13879
I'm playing with some load cells and I got a few HX711's to interface them to an Arduino and a computer. The HX711 actually has 2 channels, A and B, and there's a procedure to switch between them, but at first I thought it didn't work. Then I found that I can switch channels, but every time I do, the device slows way down--the cycle after making a channel change, there's a delay of about 60msec, so if you alternate the channels, you get a full cycle in about 120msec or roughly 8 per second. I'm wondering if I've done this right, or if there's a better procedure to make it faster.
The HX711 has its own oddball serial interface. There's a data line and a clock line, and the device does conversions repeatedly, and sends the data line low when it completes a conversion. A processor has to watch for the lowgoing edge, then send clock pulses which clock out 24 bits of actual data. You can send 1, 2 or 3 extra clock pulses, which make selections for the next cycle--channel A at a gain of 64 or 128, or channel B at a gain of 32. It's those initial lowgoing edges that seem to get slowed down by changing channels. If you don't change channels, it runs at 80 cycles per second. (Or 10, using a selection pin, but I'm trying to use 80.)