- About
- Brief information about Pmod CMPS2
- Interface Description
- Tests
- Status Information
- Issues
- Licence
Simple interface for the Digilent Pmod CMPS2 or any other module with MMC3416xPJ.
The Digilent Pmod CMPS2 is a 3-Axis Magnetometer. It contains Memsic's MMC3416xPJ 3-axis Magnetic Sensor.
Module cmps2 can be used as a simple interface for the Pmod CMPS2 (or any other module with MMC3416xPJ).
Module cmps2 offers two measurement modes. Normal measurement (initiated with measure) does a set measurement and subtracts existing offsets from measurement results. Calibration measurement (initiated with calibrate) does a reset measurement followed by a set measurement. Using these measurement results, calibrated measurement values and new offsets are calculated. Measurement results calculated via (set results - reset results) / 2 and offset values calculated via (set results + reset results) / 2.
IOs:
| Port | Type | Width | Description |
|---|---|---|---|
clk |
I | 1 | System Clock |
rst |
I | 1 | System Reset |
clkI2Cx2 |
I | 1 | I²C Clock source |
SCL* |
IO | 1 | I²C Clock Pin |
SDA* |
IO | 1 | I²C Data Pin |
x_axis |
O | 16 | Measurement result for X axis |
y_axis |
O | 16 | Measurement result for Y axis |
z_axis |
O | 16 | Measurement result for Z axis |
resolution |
I | 2 | Resolution configuration of MMC3416xPJ |
x_offset |
O | 16 | Calculated offset for X axis |
y_offset |
O | 16 | Calculated offset for Y axis |
z_offset |
O | 16 | Calculated offset for Z axis |
calibrate |
I | 1 | Initiate a measurement with a new calibration |
measure |
I | 1 | Initiate a measurement with using existing calibration |
i2cBusy |
O | 1 | Another master is using I²C bus |
valid |
O | 1 | New measurement results ready and valid |
I: Input O: Output
* contain pins _i, _o and _t
Note: Maximum frequency of clkI2Cx2 is 800 kHz, SCL will have half of this frequency.
Timing:
Time takes from initiation of new measurement and obtaining valid measurement results for diffent cases can be found at the table below.
resolution |
calibrate |
measure |
|---|---|---|
| 2'b00 (16 bit) | 15,98 ms | 7,743ma |
| 2'b01 (16 bit) | 8,927 ms | 4,217 ms |
| 2'b10 (14 bit) | 5,298 ms | 2,402 ms |
| 2'b11 (12 bit) | 3,485 ms | 1,495 ms |
(Synthesized) Utilization on Artix-7:
- Slice LUTs: 234 (as Logic)
- Slice Registers: 251 (as Flip Flop)
The CMPS2 interface module tested with test module tester_cmps2.v and constrains Basys3.xdc. I²C pins are monitored via DDiscovery. Right button connected to calibrate, left button connected to measure. Two right most switches are connected to resolution. Seven segment display is used to display x_axis, y_axis and z_axis; controled via two left most switches. Output values are also send via UART on positive edge of valid. They are send in following order: x_axis, y_axis, z_axis, x_offset, y_offset, z_offset. UART configurations are 115200, 8 bits with no parity and 1 bit stop.
Last test: 17 June 2021, on Digilent Basys 3.
- For some measurements, least significant bit of the result is wrong, resulting 0.5mG error.
CERN Open Hardware Licence Version 2 - Weakly Reciprocal