==== Level conversion ====
<wrap right>
{{:interfaces:level4.jpg?200|I2C}}
</wrap>

When interfacing between two devices such as a Raspberry
Pi with 3V3 I/O and a PICMicro running at 5V voltage level
conversion is necessary. A simple method to do this
on a breadboard is to use a pre-built adapter.

Two    popular types found on eBay
are the two channel bi-directional I2C level shifters and the four
channel general purpose converters.

=== I2C level shifter ===
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{{:interfaces:level1.jpg?200|Pickle Microchip PIC ICSP}}
</wrap>

These devices contain two mosfets with 10K pull-up resistors in the
arrangement specified by the Philips I2C interfacing application note (link below).

They also have an additional component which is a 3V3 LDO voltage regulator. This addition is to allow a 5V device to directly interface with a 3V3 device and also power it.

Although marketed for I2C they can be used for anything that demands two channels of bi-directional voltage level conversion.

== Pinout ==

<code>
3V3 OUTPUT  BVCC    AVCC  5V INPUT
3V3 CLOCK   BSCL    ASCL  5V CLOCK
3V3 DATA    BSDA    ASDA  5V DATA
GROUND      BGND    AGND  GROUND
</code>

There is a speed impact when using these device which have a slow rise time. For example, when using [[:projects:pickle|Pickle Microchip PIC ICSP]] it was found that raising the SLEEP configuration value to 8 was necessary.

=== General purpose 4 channel ===
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{{:interfaces:converter3.jpg?200|Pickle Microchip PIC ICSP}}
</wrap>

These general purpose bi-directional devices feature four mosfets in the Philips application note arrangement with 10K pull-ups.

== Pinout ==

<code>
         HV4       LV4
         HV3       LV3
         GND       GND
HIGH VCC HV        LV  LOW VCC
         HV2       LV2
         HV1       LV1
</code>

[[:projects:pickle|Pickle Microchip PIC ICSP]] was found to be more reliable when raising the SLEEP configuration value to 2 with this adapter.
=== Resources ===

{{downloads:AN10441.pdf|Level shifting techniques in I2C-bus design}}