The snippet based on SimplePie 1.3 which is already included in the package: 

Basic call: [ [ ! spiefeed ] ]

Documentation is here: http://rtfm.modx.com/display/ADDON/spieFeed

Installation Instructions

Install from Package Manager

1.6-pl

* upgraded to SimplePie 1.3

* deleted all favicon handlers due to this upgrading

Version	Released	Author	Downloads
14 Versions		1 Contributors	6,480 Downloads
1.6.2-pl	Mar, 02 2016	goldsky	632
1.6.1-pl	Oct, 22 2012	goldsky	1,280
1.5.0-pl	Feb, 01 2012	goldsky	581
1.4.0-pl	Jan, 05 2012	goldsky	306
1.3-pl	Sep, 24 2011	goldsky	453
1.2.0-pl1	May, 12 2011	goldsky	480
1.1.0-pl	Jan, 22 2011	goldsky	665
1.1.0-rc1	Dec, 30 2010	goldsky	320
1.0.0-pl	Dec, 13 2010	goldsky	315
1.0.0-rc2	Dec, 06 2010	goldsky	291
1.0.0-beta2	Oct, 18 2010	goldsky	320
1.0.0-beta1	Oct, 18 2010	goldsky	256
1.0.0-rc1	Oct, 16 2010	goldsky	232