atmegaavrencoderinterfacemotor
I'm trying to interface an HEDS 9700 optical encoder using an HCTL-2020 IC (or anything else) with my Atmega ( atmega128, atmega32, atmega16, atmega8 or any AVR-family based microcontroller, don't matter for me ).
But I don't know what should I do. I read datasheets of both devices. What pins from HCTL must connected to my microcontroller (and which one ?) ? Basically, I don't know what to do with this encoder.
Please help me find out the way.
Thanks.
CKSEL typically stands for clock select. There are several choices that can be selected via an internal multiplexer-- some for test, others for alternate sources.
Since you are using a xtal, you can provide the code to select that option: which are in the first 2 rows of p 26. You can use 3 bottom rows of table 4 for a crystal. Each is tuned to a particular range of frequencies as shown.If your crystal reference was design to oscillate around 4MHz, you would set the sel bits to code, 111, for example. 16Mhz only works with CKOPT low using any of the three select codes shown in row 4 of the table.
External caps should be 12-22pF not 22uF for the xtal according to the same table. It also only specifies a max oscillator limit of 16MHz, so I would not use a 20MHz xtal.
Looks to me like the watchdog timer functionality is internal.
*note xtal and crystal are used synonymously here.
A quick experiment with a piezoelectric bender shows the following voltages:
Assuming the area of interest spans the first 4 levels of signal, and any reading higher than 10 Volts can be generalized to an arbitrary "Out-of-Range" reading, the following implementation should serve for the purposes of question:
simulate this circuit – Schematic created using CircuitLab
The diode D1 shunts the negative portion of the signal that the peizo bender will generate on knocks or release of pressure. To be extra-cautious, this can be substituted by a Schottky diode to cope with very fast spikes, or for tighter clipping to ground rail (~ 0.3 Volts instead of ~0.7 Volts), a germanium diode.
The Zener diode is intentionally selected as 4.7 Volts, in order to ensure that the output voltage does not overshoot 5 Volts under any circumstances.
The op-amp buffer ensures that the voltage divider is not significantly loaded by the ADC pin, hence the voltage divider resistance computation is simplified.
This circuit will output half the positive voltage generated by the piezoelectric pressure sensor until the voltage reaches approximately 4.7 Volts, then clamp at that voltage for any higher pressures applied. Any negative voltage generated due to knocks or sensor bounce-back, will be shunted across the diode D1, protecting the op-amp (or the ADC if directly connected) from negative voltages.
Best Answer
If your encoder doesn't pulse too fast I'd do it without the HCTL-2020. There's nothing in it a microcontroller can't do.
The HCTL-2020 is a parallel output device, for interfacing with an 8-bit microprocessor bus (probably from the Crimean War period). Data is on D0-D7 if the OE input is low. Since you have 12/16 bit of data you'll have to use the SEL input to select whether you want the HOB (High Order Byte) or the LOB (Low Order Byte). Use the RST input to reset the counter.
So OE, SEL and RST are outputs from the microcontroller, D0-D7 are inputs.
The HCTL-2016 outputs 2 square wave signals in quadrature, which is needed to tell the rotation direction. These go to the CH A and CH B inputs of the HCTL-2020. If you want to connect the 2016 directly to a microcontroller (saves you 9 I/O pins) you'll want them on pins which can give interrupts on changes.